Based on https://www.etymonline.com/word/restaurateur https://www.etymonline.com/word/restaurateur and https://parisfoodhistory.blogspot.com/2018/06/what-were-v

Based on https://www.etymonline.com/word/restaurateur https://www.etymonline.com/word/restaurateur and https://parisfoodhistory.blogspot.com/2018/06/what-were-very-first-restaurants-like.html https://parisfoodhistory.blogspot.com/2018/06/what-were-very... is seems the choice of wording was one part legal hack and one part marketing gimmick. TL;DR: Apparently only traiteurs were permitted to sell meals. Restaurants were marketed as a kind of (I guess) upscale health service, originally only selling fancy broths. One of the early restaurateurs is documented as using the advertisement, "Venite ad me omnes qui stomacho laboratis, & ego restaurabo vos" ("Come to me, all of you whose stomachs are in distress, and I will restore you", an allusion to Matthew 11:28, "Come to Me, all of you who are weary and burdened, and I will give you rest.")