Green’s Dictionary of Slang

1. a friend; thus honest cod, a good friend.

1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk I 151: Come, my cod, let me coll thee till I kill thee. [Ibid.] 5:XV: The old fusty landlady kepty her ground, swearing like any butter-whore that the tarpaulins were very honest cods.
1696		Motteux (trans.) Gargantua and Pantagruel (1927) II Bk V 517: What good bub! what dainty cheer! O what an honest cod was this same Ædituus.

2. a fellow .

c.1688		‘The Wife’s Answer to the Henpeckt Cuckold’s Complaint’ in Ebsworth Roxburghe Ballads (1891) VII:2 433: But I will jerk and firk [t]his Cod, and make the Rogue’s buttocks blew.
c.1698		B.E. Dict. Canting Crew.
1713		W. King York Spy 33: Since you the Noble Malt abuse [...] May all true Cods you Ale refuse.

3. a fool [? cod’s head n.].

c.1698		B.E. Dict. Canting Crew n.p.: Cod [...] a Fool. A meer Cod, a silly, shallow Fellow. [...] A jolly or lusty Cod, c. the same. An honest Cod, a trusty Friend.
1725		New Canting Dict.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict.
1835		G. Kent Modern Flash Dict. 10: Cod – haughty meddling fool.
1841		‘The Frisky Family’ in Gentleman Steeple-Chaser 35: When she threw all the balls she prov’d ’em all cods.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1909		J. Ware Passing Eng. of the Victorian Era 82/2: Cod (Printers’). A fool; e.g., ‘the fellow’s a cod’.
c.1914		C. Mac Garvey Green Line and the Little Yellow Road in Mac Thomáis (1982) 159: Now Jamesy shut your gob, t’was blooming rotten job / To take that barefaced Johnnie for a Cod.
1925		S. O’Casey Shadow of a Gunman Act I: If you want to make a cod of anybody, make a cod of somebody else.
1939		‘Flann O’Brien’ At Swim-Two-Birds 217: He’s only an old cod.
1942		S. O’Casey Red Roses for Me Act I: What’s in this Ruskin of yours but another oul’ cod with a gift of the gab?
1948		J. O’Connor Come Day – Go Day (1984) 20: Don’t act the cod, Tom.
1951		S.H. Bell December Bride 265: The ould cod means no harm.
1961		(con. 1890–1910) ‘Flann O’Brien’ Hard Life (1962) 100: That’s the sort of cods we have looking after law and order in Dublin.
1979		H. Leonard A Life (1981) Act I: You’re a cod.
1988		R. Doyle Commitments 39: Cuntish cod, said Deco.
1992		P. McCabe Butcher Boy (1993) 33: Carrying on with her like a schoolboy halfwit. The whole town knows that too, made a cod of himself with her.
2001		P. McCabe Emerald Germs of Ireland 355: Pat, you auld cod you! I’m only pretending to be investigating!