"The practice of tipping began in Tudor England. In medieval times, tipping was a master-serf custom wherein a servant would receive extra money for having performed superbly well. By the 17th century, it was expected that overnight guests to private homes would provide sums of money, known as vails, to the host's servants. Soon afterwards, customers began tipping in London coffeehouses and other commercial establishments".

https://en.m.wikipedia.org/wiki/Gratuity