Translate Search function


I use “Say What?” for translation, it work fine but I’ve a probem to translate the widget term “Search…”.

I see 2 closed topics on this subject but there isn’t the entire soluce.

I use Illdy theme with the last wordpress. The settings are :
Original string : Search
Text domain : illdy
Replacement string : Recherche

I think Text domain is not good.

Thanks for all your work and disponibilty
Sorry I’m newbie and my english is bad