I believe the Water Margin reference is Liang-Shan Po, which refers to the marsh where the outlaw heroes hid and took as their groups' name. It's kind of a Chinese Robin Hood affair but with more martial arts.

I have a few idioms (idia?) of my own. All of my family know what "Shuv t'wud in th'ole!" means, as well as "Was tha born in a field wi' t'gate oppen?" My increasingly lanky eldest granddaughter is now accustomed to being addressed as "Tha greet long streak o' yesterdays' dishwatter!"

An object of which I have temporarily forgotten the name is an 'oojah'. A tool or device in the same situation is an 'oojah-cum-spiflicator'.

Others include:

Dim as a Toc-H lamp.

Neither fish, flesh, fowl nor good red herring.

You dirty rotten swine!

Go ahead, make my day.

That's a Japanese tissue paper job.

That's going to hurt in the morning.

Spectacles, testicles, wallet and watch.

Listen very carefully, I shall say this only once!

Gid Moaning!

Make it so.

The engines cannae take it.

Ye cannae change the laws of physics

You are young, Grasshopper, but you will learn

I suspect the origins and/or meanings of most of these are obvious!