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Hi,

tip someone off -
to warn someone secretly about something that will happen, so that they can take action or prevent it from happening.

Does anyone know the phrase's origin? (i.e. from its literal meaning to its figurative meaning)

Thanks,
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This is all I could find, MTL:

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.
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Hi Mr. M,

Thanks for your info.

I still have some confusions. You might know the answers.

1. 'Tip' and 'tap' sounds similar and they have quite similar meaning in the scope of our discussion.

tap - to listen secretly to someone's telephone by using a special piece of electronic equipment

tip - to give a piece of secrete information

Do you happen to know who borrows who's meaning? Or the two words have a similar meaning just by coincidence?


2. Do you happen to know what 'off' means in 'tip someone off'? Can you find some other similar meaings with this particular usage? (i.e. V + OFF)

Thanks,
#1 -- I think it's just a coincidence. They seem to come from different 'taps', both branching off early.

For 'tap', the meanings in question are:

'To furnish with a spigot or tap.
To pierce in order to draw off liquid: tap a maple tree.
To draw (liquid) from a vessel or container: tap a new keg of beer.
Medicine. To withdraw fluid from (a body cavity).
To make a physical connection with or open outlets from: tap a water main.
1. To wiretap (a telephone).
2. To establish an electric connection in (a power line), as to divert current secretly.
To establish access to or a connection with: tapped a new market for inexpensive books.
To take advantage of; make use of: tapped voter anger to win the election. '

'tap (n.) (Dictionary.com):
"stopper, faucet," O.E. tæppa, from P.Gmc. *tappon (cf. M.Du. tappe, Du. tap, O.H.G. zapfo, Ger. zapfen). Originally a tapering cylindrical peg (hence taproot, 1601). Meaning "device to listen in secretly on telephone calls" is from 1923, from the verb in this sense, originally (1869) with ref. to telegraph wires. Phrase on tap "ready for use" is recorded from 1483. The verb meaning "to supply with a tap" is from O.E. tæppian. Extended sense of "make use of" is first recorded 1575. Tap-room is from 1807. Tapped out "broke" is 1940s slang, perhaps from the notion of having tapped all one's acquaintances for loans already (cf. British slang on the tap "begging, making requests for loans," 1932).'

For 'tip', as I posted before:

tip (v.2) (Dictionary.com):
"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.

As for definitions, perhaps your idiom is related to:

To touch or raise (one's hat) in greeting.
To reveal one's resources or intentions (tip (one's) hand)

#2 -- I leave to someone else or myself later. I have to teach soon.