Green’s Dictionary of Slang

bill n.¹

1. the penis.

[1654		Mercurius Fumigosus 6 5 July 48: Where she soon venter’d on her prey, / And worm’d her Cull at Billyeard play].
1727		‘The Martin and the Oyster’ in 18C Collections Online 🌐 You Jade, said he, behold my Bill, / See how erect it stands; ’Twas made for Pleasure.

2. (Aus./US) the nose.

1834		W.A. Caruthers Kentuckian in N.Y. II 208: I’ve been poppen my bill into it, and out of it again, like a kingfisher in a mill-dam.
1910		Truth (Brisbane) 3 July 8/5: You can see by his ‘bill’ — that's a slang term for nose— / ( He can smell a beef steak on the table.
1935		Z.N. Hurston Mules and Men (1995) 45: You hear dese har ole coons lyin’ up a nation and you stick in yo’ bill.
1952		R.C. Ruark 27 June [synd. col.] There is no shortage of fighters. The GI Bill of Rights allowed a lot of impoverished [ex-soldiers] to get educated instead of getting their bills busted [W&F].

In phrases

bill in (v.)

to butt in, to interrupt.

1938

D. Runyon ‘A Piece of Pie’ in Runyon on Broadway (1954) 674: Pardon the intrusion, and excuse me for billing in.