Green’s Dictionary of Slang

cod adj.

[cod v. (2) + ? play on fishy adj.2 (1); note theatrical jargon cod version, a burlesque of a well-known play]

1. fake, parodic; usu. in comb., e.g. cod-Russian, cod-typewriter etc.

[UK]Era 12 May 19/1: Prof. Roscoe, a ‘cod’ clairvoyant.
[UK]H. Livings Nil Carborundum (1963) Act III: [We hear Neville’s voice in the stillness, in a cod-Indian wail:] Sixteen annas make one rupee / Seventeen annas one buckshee.
[UK]J. Sullivan ‘Go West Young Man’ Only Fools and Horses [TV script] (Speaking in cod Aussie).
[UK]Guardian Guide 10–16 July 9: Both are cod attempts to tell the story of The Bible.
[UK]Indep. Rev. 19 Apr. 1: Here he adopts a cod North African accent.
H. Mantel Assassination of Thatcher 227: I don’t think you should sneer at my great-uncles for being cod-Irish.

2. a general negative.

[UK]R. Hauser Homosexual Society Appendix 3, 167: Cod, vile.
[US]B. Rodgers Queens’ Vernacular 52: cod (Brit gay sl, fr sl cod= to hoax) vile ‘I do beg your’s, you huffy cod bitch!’.
House & Home 9-10 Oct. 1/2: Cod psychology would doubtless put this down to his childhood.
[UK]P. Baker Fabulosa 290/2: cod bad.

In derivatives

coddy (adj.)

(Polari) second-rate, amateurish.

[UK]P. Baker Fabulosa 290/2: coddy, cody bad, amateurish.
[UK]R. Milward Man-Eating Typewriter 4: I am a meese omi and a coddy auteur to boot. My achievements [...] have not been up to dick.