Twitter Block translation
Do you have French language on you site? 
You should not change code of contrib modules. You can override, extend it in your custom module.
If you have fr  language on site , back t() with EN labels, go to admin/config/regional/translate/translate try to search EN labels and translate them.




Another way to get translations, use module l10n_update, it can get translation if they available on Localization servers.