Origin Of The Idioms

[ParaVoz]

PLEASE HELP ME!!!!!
I need your help urgently!!!!! I am writing an essay about the origin of English idioms. I have already found some information but i still have a lot of questions.
1. origin of an idiom: looks like something a cat dragged in
2. origin of an idom: as much use as a chocolate fireguard
I walso would like to know your opinion about English idioms and their origin in general. i will also be glad to see an advise on this subject
Please answer as quick as possible. The conference that i am getting prepared starts in 2 weeks!!!!

[Anglika]

To look like something the cat dragged in = something that a cat has caught and has dragged home will be mangled and mutilated.

As much use as a chocolate fireguard = a fireguard is a protective mesh put in front of an open burning fire. One made of chocolate would melt. So it would not be of much use.