tip (v.1) Look up tip at Dictionary.com
c.1300, "to knock down, overturn, topple, knock askew" (transitive), of uncertain origin, possibly from Scandinavian (compare Swedish tippa "to tip, dump"), or from a special use of tip (n.). Intransitive sense of "to fall over, be overturned" is from mid-15c. Related: Tipped; tipping. To tip the scales at "weigh (so much" is from 1879. Tipping point attested by 1972. To tip (one's) hand "reveal one's intentions" is from 1907, an image from poker-playing.
tip (n.1) Look up tip at Dictionary.com
c.1400, "extreme end of something, top of something round or pointed, metal attachment to the end of something," from Middle Low German or Middle Dutch tip "utmost point, extremity, tip" (compare German zipfel, a diminutive formation); or from a Scandinavian source (compare Old Norse typpi).
tip (v.2) Look up tip at Dictionary.com
"give a small present of money to," c.1600, originally "to give, hand, pass," 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 noun meaning "piece of confidential information" is from 1845; and the verb in the sense "give private information to" is from 1883.

The popularity of the tale of the word's supposed origin as an acronym in mid-18th century English taverns seems to be no older than Frederick W. Hackwood's 1909 book "Inns, Ales and Drinking Customs of Old England," where it was said to stand for To insure promptitude (in the form to insure promptness the anecdote is told from 1946). A reviewer of the book in the "Athenaeum" of Oct. 2, 1909, wrote, "We deprecate the careless repetition of popular etymologies such as the notion that "tip" originated from an abbreviated inscription on a box placed on the sideboard in old coaching-inns, the full meaning of which was "To Insure Promptitude." Also see here.
tip (v.3) Look up tip at Dictionary.com
c.1200, "to strike, occur suddenly," of uncertain origin, possibly from Low German tippen "to poke, touch lightly," related to Middle Low German tip "end, point," and thus connected to tip (n.); or else related to tap (v.1). Meaning "strike sharply but lightly" is from 1560s. Sports sense is from 1816, originally in cricket. Related: Tipped; tipping.
tip (n.2) Look up tip at Dictionary.com
"a light, sharp blow or tap," mid-15c., from tip (v.3).
tip (v.4) Look up tip at Dictionary.com
"put a tip on, adorn with a tip," late 14c., from tip (n.) or Old Norse typpa. Related: Tipped; tipping.