Green’s Dictionary of Slang

1. tossing three coins in a hat in order to determine who pays for drinks; he who guesses right is exempt from payment.

1821		Egan Life in London (1869) 314: [note] Gaffing was for him unfortunately introduced; and before long [...] poor — was completely cleaned out.
1828		G. Smeeton Doings in London 39: That man [...] is a notorious fellow at Gaffing.
1831		Satirist (London) 13 Nov. 253/3: some were not idle in applying themselveto the delights of a game called gaffing [...] Jerry Hawthorn [...] won about twelve pounds.
1846		Swell’s Night Guide 120/1: Gaffing, tossing with the piemen.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict. 171: Gaffing tossing half-pence, or counters [...] One man tosses, and another calls. Sometimes the coins are tossed from a stick, and the tosser keeps those which fall heads uppermost.
1882		Sydney Sl. Dict. (2 edn) 4: Gaffing - Tossing.
1895		Crowe Aus. Sl. Dict. [as1882].
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 87: ‘A gaffing joint’ is a gambling house.
1911		A. Wright Gamblers’ Gold (1931) 111: Started a gaffin’ school on th’ railway job.

2. coin-tossing, pitch-and-toss.

1859, 1860

Hotten Dict. of Modern Sl. etc.