Where did the word Tip come from?

Tip as an acronym appears to have three primary "explanations," NONE of them valid:

* To Insure Promptness

* To Insure Performance

* To Insure Prompt Service

According to Snopes:

"Tip is an old Word, and it has nothing to do with either acronyms or the act of attempting to influence quality of service. Although the Word has many meanings, both as a verb and as a noun, the use of the term as it applies to monetary rewards to servants dates to the 1700s. It first appeared in this context as a verb ("Then I, Sir, tips me the Verger with half a Crown" from the 1706 George Farquhar play The Beaux Stratagem) and was first recorded as a noun in 1755. However, the use of tip to describe the act of giving something to another (where that list of possible 'somethings' could include small sums of money, intelligence on horse races, or the latest silly joke) goes back to 1610. Tip slipped into the language as underworld slang, with the verb 'to tip' (meaning 'to give to or share with') being used by shady characters as part of the then-current argot of petty criminals."