Green’s Dictionary of Slang

1. to stay, to hide out.

1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 76: I might just coch at my yard with a big head of herb and feel merry.
2001		(con. 1981) A. Wheatle East of Acre Lane 209: She mus’ be coching wid one of her friends.

2. to lean on.

1999

(con. 1979–80) A. Wheatle Brixton Rock (2004) 154: She coched her head on her brother’s chest as he stared into space.

3. to move without being seen.

2003

Guardian 13 Sept. 26/4: The street language of Dizzee and his peers evolves daily: ‘coch’ means to move undetected.