If you call this with argument "unused=true" it searches for the translation strings that exist in en_US but are never used.
IMPORTANT: that can take quite a lot of time (up to 10 minutes), you need to tune the max_execution_time on your php.ini accordingly.

Duplicate strings in lang files in /home/booka/www/dolibarr/dev/translation/../../htdocs/langs/en_US/ - 96 found

#StringFile and lines
1ShowAccountingJournalaccountancy.lang (96 - Show accounting journal) (311 - Show accounting journal)
27FeatureNotAvailableWithReceptionModuleadmin.lang (2073 - Feature not available when module Reception is enabled) (2078 - Feature not available when module Reception is enabled)
32NewAssetTypeassets.lang (24 - New asset type) (65 - New asset type)
52ErrorRefAlreadyExistserrors.lang (11 - Reference <b>%s</b> already exists.) (82 - Ref used for creation already exists.)
56NotTheAssignedApproverholiday.lang (77 - You are not the assigned approver) (101 - You are not the assigned approver)
59Language_es_GTlanguages.lang (36 - Spanish (Guatemala)) (45 - Spanish (USA))
89unitGproducts.lang (205 - Gram) (213 - Gram)
90unitMproducts.lang (206 - Meter) (217 - Meter)
91unitM2products.lang (208 - Square meter) (223 - Square meter)
92unitM3products.lang (209 - Cubic meter) (229 - Cubic meter)
93Receptionreceptions.lang (4 - Reception) (7 - Reception)
94Receptionsreceptions.lang (5 - Receptions) (8 - Receptions)
96ImportSitewebsite.lang (76 - Import website template) (120 - Import website)
3ByYearaccountancy.lang (217 - By year)
main.lang (811 - By year)
29Eventsagenda.lang (12 - Events)
main.lang (922 - Events)
41ShowDetailsblockedlog.lang (16 - Show stored details)
main.lang (1085 - Show details)
45Browsercashdesk.lang (92 - Browser)
main.lang (730 - Browser)
50StatusToPaycompta.lang (66 - To pay)
main.lang (436 - To pay)
58StatusInterInvoicedinterventions.lang (30 - Billed)
main.lang (524 - Invoiced)
61Closedmain.lang (148 - Closed)
ticket.lang (67 - Closed)
62ConfirmCloneAskmain.lang (182 - Are you sure you want to clone the object <b>%s</b>?)
supplier_proposal.lang (38 - Are you sure you want to clone the price request <b>%s</b>?)
63Typemain.lang (230 - Type)
ticket.lang (71 - Type)
64MulticurrencyPaymentAmountmain.lang (379 - Payment amount, original currency)
multicurrency.lang (19 - Payment amount, original currency)
65OpenAllmain.lang (528 - Open (All))
stocks.lang (169 - Open for all actions)
66Rejectsmain.lang (543 - Rejects)
withdrawals.lang (40 - Rejects)
6InternalUseradmin.lang (51 - Internal user)
users.lang (70 - Internal user)
7NewModuleadmin.lang (214 - New module)
modulebuilder.lang (8 - New module)
8NoticePeriodadmin.lang (275 - Notice period)
holiday.lang (113 - Notice period)
9LanguageFileadmin.lang (375 - Language file)
modulebuilder.lang (51 - File for language)
10PriceFormatInCurrentLanguageadmin.lang (416 - Price Format In Current Language)
companies.lang (30 - Price display format in the current language and currency)
11Stringadmin.lang (417 - String)
members.lang (104 - String)
12Intadmin.lang (422 - Integer)
members.lang (106 - Int)
13DateAndTimeadmin.lang (424 - Date and hour)
members.lang (107 - Date and time)
14Fieldadmin.lang (506 - Field)
blockedlog.lang (2 - Field)
exports.lang (62 - Field)
15Upgradeadmin.lang (1098 - Upgrade)
install.lang (104 - Upgrade)
16Serveradmin.lang (1109 - Server)
install.lang (49 - Server)
17DatabaseServeradmin.lang (1111 - Database host)
install.lang (52 - Database server)
18DatabaseNameadmin.lang (1112 - Database name)
install.lang (53 - Database name)
19DriverTypeadmin.lang (1120 - Driver type)
install.lang (48 - Driver type)
20CompanyNameadmin.lang (1141 - Name)
companies.lang (25 - Company name)
21WithdrawalsSetupadmin.lang (1649 - Setup of module Direct Debit payments)
withdrawals.lang (36 - Direct debit payment setup)
22Buyadmin.lang (1731 - Buy)
products.lang (56 - Purchase)
23Selladmin.lang (1732 - Sell)
products.lang (55 - Sell)
24AccountancyCodeadmin.lang (1735 - Accounting Code)
companies.lang (318 - Accounting account)
25CashDeskadmin.lang (1759 - Point of Sale)
cashdesk.lang (3 - Point of sale)
26ByDefaultInListadmin.lang (1918 - Show by default on list view)
categories.lang (94 - By default in list)
2LineIdaccountancy.lang (136 - Id line)
exports.lang (43 - Id of line)
4CustomerInvoicePaymentaccountancy.lang (234 - Payment of invoice customer)
banks.lang (104 - Customer payment)
5NotReconciledaccountancy.lang (300 - Not reconciled)
banks.lang (103 - Not reconciled)
28AffectedToagenda.lang (10 - Assigned to)
projects.lang (118 - Allocated to)
30Locationagenda.lang (16 - Location)
stocks.lang (39 - Location)
31InterventionSentByEMailagenda.lang (84 - Intervention %s sent by email)
interventions.lang (38 - Intervention %s sent by email)
33DeleteTypeassets.lang (29 - Delete)
members.lang (79 - Delete)
34ShowTypeCardassets.lang (32 - Show type '%s')
members.lang (148 - Show type '%s')
35Settings assets.lang (43 - Settings)
recruitment.lang (29 - Settings)
36IBANbanks.lang (32 - IBAN number)
bills.lang (443 - IBAN)
37BICbanks.lang (33 - BIC/SWIFT code)
bills.lang (446 - BIC/SWIFT)
38Accountbanks.lang (67 - Account)
compta.lang (15 - Account)
39SubscriptionPaymentbanks.lang (106 - Subscription payment)
members.lang (162 - Subscription payment)
40InvoiceRefbills.lang (325 - Invoice ref.)
receiptprinter.lang (67 - Invoice ref)
42NoSupplierOrderboxes.lang (75 - No recorded purchase order)
orders.lang (80 - No purchase order)
43ShowCompanycashdesk.lang (30 - Show company)
companies.lang (334 - Third Party)
44Historycashdesk.lang (70 - History)
suppliers.lang (6 - History)
46DeleteFromCatcategories.lang (85 - Remove from tags/category)
compta.lang (251 - Remove from accounting group)
47Customercommercial.lang (4 - Customer)
companies.lang (278 - Customer)
48Prospectcommercial.lang (6 - Prospect)
companies.lang (276 - Prospect)
propal.lang (12 - Prospect)
49ShowTaskcommercial.lang (18 - Show task)
projects.lang (39 - Show task)
51ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (84 - Closed)
53ExportsAreaexports.lang (2 - Exports)
other.lang (264 - Exports area)
54ExportableDatasexports.lang (6 - Exportable dataset)
other.lang (268 - Exportable data)
55AvailableFormatsexports.lang (27 - Available Formats)
other.lang (265 - Available formats)
57CreateUserinstall.lang (60 - Create user account or grant user account permission on the Dolibarr database)
users.lang (30 - Create user)
60Answeredmails.lang (174 - Answered)
ticket.lang (65 - Answered)
67OrderDateorders.lang (10 - Order date)
suppliers.lang (9 - Order date)
68CreatedByother.lang (113 - Created by %s)
ticket.lang (157 - Created by)
69FollowingUrlAreAvailableToMakePaymentspaybox.lang (4 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
stripe.lang (5 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
70PaymentFormpaybox.lang (5 - Payment form)
stripe.lang (6 - Payment form)
71WelcomeOnPaymentPagepaybox.lang (6 - Welcome to our online payment service)
stripe.lang (7 - Welcome to our online payment service)
72ThisScreenAllowsYouToPaypaybox.lang (7 - This screen allow you to make an online payment to %s.)
stripe.lang (8 - This screen allow you to make an online payment to %s.)
73ThisIsInformationOnPaymentpaybox.lang (8 - This is information on payment to do)
stripe.lang (9 - This is information on payment to do)
74ToCompletepaybox.lang (9 - To complete)
stripe.lang (10 - To complete)
75YourEMailpaybox.lang (10 - Email to receive payment confirmation)
stripe.lang (11 - Email to receive payment confirmation)
76Creditorpaybox.lang (11 - Creditor)
stripe.lang (13 - Creditor)
77PaymentCodepaybox.lang (12 - Payment code)
stripe.lang (14 - Payment code)
78Continuepaybox.lang (15 - Next)
stripe.lang (17 - Next)
79AccountParameterpaybox.lang (19 - Account parameters)
stripe.lang (27 - Account parameters)
80UsageParameterpaybox.lang (20 - Usage parameters)
stripe.lang (28 - Usage parameters)
81InformationToFindParameterspaybox.lang (21 - Help to find your %s account information)
stripe.lang (29 - Help to find your %s account information)
82CSSUrlForPaymentFormpaybox.lang (23 - CSS style sheet url for payment form)
stripe.lang (31 - CSS style sheet url for payment form)
83Stockproducts.lang (51 - Stock)
stocks.lang (18 - Stock)
84Stocksproducts.lang (53 - Stocks and location (warehouse) of products)
stocks.lang (19 - Stocks)
85Movementsproducts.lang (54 - Movements)
stocks.lang (27 - Movements)
86Suppliersproducts.lang (89 - Vendors)
suppliers.lang (2 - Vendors)
87ListOfStockMovementsproducts.lang (96 - List of stock movements)
stocks.lang (30 - List of stock movements)
88Unitproducts.lang (179 - Unit)
stocks.lang (46 - Unit)
95NewUserticket.lang (281 - New user)
users.lang (29 - New user)