"up the spout"

Does somebody know where the phrase "up the spout" or "shove it up the spout" comes from? I've been seeing a lot in P.G. Wodehouse to refer to pawning something and was wondering where it came from.

I saw a few references stating that "spout" used to mean the device ( lift, for those in Blair Land ) used in a pawnshop for sending deposited articles up for storage.

So if anything - or, by transference, anybody - is up the spout, there are difficulties.

Is the mirror image of this called "going down the tubes"?

The phrase 'up the spout' can also mean pregnant (in the UK at least) though I am sure that Wodehouse never used it to mean that.

DFG