Green’s Dictionary of Slang

1. (also twang) the penis.

1598		Florio Worlde of Wordes n.p.: Tempella, a fiddle [...] Also a great swaggering twanger, a horse toole, a great dildo, or good pricke.
1611		Florio Queen Anna’s New World of Words n.p.: Tempella [...] a huge twanger, a swagring toole, a filthy dildoe.
1632		R. Brome Covent-Garden Weeded I i: Were you but now all o’th heigh to set your self out for a signe with your fiddle cum twang, and promise such wonders, forsooth, and will not now be seen.
1890–1904		Farmer & Henley Sl. and Its Analogues.

2. (also twangler, twanker) something very large or fine of its kind.

1594		Lyly Mother Bombie V iii: What a mischief make the twanglers here.
1672		J. Phillips Maronides (1678) VI 14: Your old friend Juno full of rancour, / Shall never dfail ye with a Twanker.
1877		E. Peacock Gloss. of . . . Manley & Corringham 581: Twanger, a barefaced lie .
1889		E. Peacock Gloss. of . . . Manley & Corringham (2nd edn) 589: Them to’nups e’ th’ foherteen aacre is twangers .

3. a lie.

1849

Sam Sly 24 Mar. 2/1: Mr. H. R—n—on [...] not to tell the young lady to whom he is paying attentions’ such abominable ‘twangers’.

4. (Aus.) the vagina.

1996

(con. 1964-65) B. Thorpe Sex and Thugs and Rock ’n’ Roll 7: She didn’t flash her twang like that for just anyone.