The noun 'tip-off' is a direct nominalization of the phrasal verb 'to tip off', meaning to give someone a discreet warning or piece of information. The verb 'tip' in this sense emerged in the 17th century, with its origin obscure but possibly linked to the idea of a light, covert touch or nudge, as in giving a subtle hint. The particle 'off' completes the action, implying the information is passed from the informant to the recipient. By the early 20th century, this verbal action was solidified into the noun 'tip-off', specifically entering the lexicon of law enforcement and journalism to denote the confidential information itself, while also developing a distinct meaning in sports for the initial jump ball in basketball.

Structure: tip (to give a small piece of advice) + off (away, from) - tip (verb): From Middle English tippen, of uncertain origin, possibly from Old Norse or Low German. In this compound, it functions as the core verb meaning 'to give a hint or private information'. - off (adverb/preposition): From Old English of, off, of Germanic origin. In this compound, it functions as an adverbial particle completing the phrasal verb, suggesting the act of giving information away or from a source.