Indeed. I think it goes back much further too. Restaurants are basically a 200 year-old technology, but rich people dining well when visiting each others' coun

Indeed. I think it goes back much further too. Restaurants are basically a 200 year-old technology, but rich people dining well when visiting each others' country houses goes back a lot further. And I believe it was the custom that, on departing, a visitor would tip the host's servants. It's my impression that this is where the custom came from (but not an expert opinion).