ein Akronym?
dürfen wir raten?
(erster Versuch: take it, please)

Der Merriam-Webster hat nur eine Vermutung, keine Sory:

Main Entry: 9tip
Function: verb
Inflected Form(s): tipped; tip·ping
Etymology: perhaps from 6tip
transitive verb
1 : GIVE, PRESENT
2 : to give a gratuity to
intransitive verb : to bestow a gratuity

Main Entry: 6tip
Function: verb
Inflected Form(s): tipped; tip·ping
transitive verb
1 : to strike lightly : TAP
2 : to give (as a baseball) a glancing blow

http://www.m-w.com/cgi-bin/dictionary

Ebenfalls keine Story, aber die gleiche Vermutung, hat der Online Etymology Dictionary (wie der Merriam-Webster über das kleine "i" vor "tip" von LEO aus verlinkt:

tip (v.2)
"give a small present of money to," 1610, "to give, hand, pass," originally thieves' cant, perhaps from tip (v.3) "to tap." The meaning "give a gratuity to" is first attested 1706. The noun in this sense is from 1755; the meaning "piece of confidential information" is from 1845; the verb in this sense is from 1883; tipster first recorded 1862.
tip (v.3)
"light, sharp blow or tap," c.1466, possibly from Low Ger. tippen "to poke, touch lightly," related to M.L.G. tip "end, point," and thus connected to tip (n.); or else connected with tap (v.) "to strike lightly." The noun in this sense is attested from 1567.

http://www.etymonline.com/index.php?term=tip

tip is not an acronym, AFAIK. Table is perfect, to improve performance, to insure promptness: all are fun backronyms.

to improve promtnes

back in the day, it used to be the other way around. you tipped before you received drinks and/or drinks just to make sure you were priortized...

simple as that

promptness

*sorry