Bobbins - Cockney rhyming slang

I've known the word "bobbins" for quite a while. It is largely used in the North of England and the wondrously crazy Frank Sidebottom used to say it a lot.

Frank Sidebottom, he's just seen something bobbins.

Bobbins means anything of a poor quality, but the root of the word is in Cockney rhyming slang, here's a clue.

Bobbins of cotton is rhyming slang for rotten, which is odd as bobbins are "reely" good.