Green’s Dictionary of Slang

1. used to address an otherwise unknown male.

1899–1900		C.L. Cullen Tales of the Ex-Tanks 43: Hey, Bill [...] just shoot us out to the fight, will you?
1919		Wodehouse Damsel in Distress (1961) 31: ‘And what,’ he inquired suavely, leaning a little further out of the cab, ‘is eating you, Bill?’.

2. (Aus.) generic for an Aus. soldier.

1900

Bulletin (Sydney) 13 Jan. 20/2: Why they were so much gladder at being relieved by the Australian Bill than by the British Tommy isn’t explained, but it seems they almost fell down dead with joy.

3. (US gay) generic for a masculine male homosexual or a mannish lesbian.

1972

B. Rodgers Queens’ Vernacular 31: Bill 1. Masculine male homosexual [...] 2. sarcastic title for one who claims to be masculine ‘Get you, Bill, in that butch marine drag’ 3. (kwn LV, les sl, mid ’60s) banter term between mannish lesbians ‘Hey, Bill, who was that redhead in your bed this morning?’.