Green’s Dictionary of Slang

1. deception, deceit, a lie; thus cod-acting, foolish behaviour.

1891		Albert Chevalier ‘The Cockney Tragedian’ 🎵 I taught ’em what I knew, which they declared was simply ‘cod’ And all I got for teachin’ ’em was eighteen months in quod.
1912		Sport (Adelaide) 6 Jan. 8/4: No cod he is a champion — but not at fishing.
1916		Joyce Portrait of the Artist as a Young Man 230: Marx is only a bloody cod.
1937		J. Curtis You’re in the Racket, Too 220: It had been all cod what he had said last night.
1942		S. O’Casey Red Roses for Me Act II: He stopped to tell a couple of railwaymen that the Story of Adam an’ Eve was all a cod.
1955		J.P. Donleavy Ginger Man (1958) 197: ‘It’s great for sore throats.’ ‘Cod.’.
1989		H. Leonard Out After Dark 100: I knew it to be a cod of a yarn.
1997		C. McPherson Weir 53: Don’t be giving me that old cod now.

2. (orig. Irish) a joke, a hoax, a leg-pull, a parody.

1916		Joyce Portrait of the Artist as a Young Man 19: I didn’t mean to, honour bright. It was only for cod. I’m sorry.
1948		P. Kavanagh Tarry Flynn (1965) 70: He had the sleeper ready to take away, had it over the paling and was going back for another – the greedy dog – when I snaffled it on him. Just for a cod, you know.
1954–56		B. Behan ‘The Same Again, Please’ in After the Wake (1981) 106: ‘I will,’ said I. ‘In the cod or in the real?’ ‘The real,’ said I.
1972		(con. 1930s–40s) N. Conway Bloods 74: One never knew whether his initial order was real or ‘in cod’.
1997		C. McPherson Weir 39: It was only a cod, sure.