Why are firemen called "jakes"?

Just wondering…what is the origin of this term-is it short for “jacob’s Ladder” (from the Bible? :confused:

Dunno about firemen, but urbandictionary.com says:

That last guess is probably urban mythology.

Where did you see it applied to firemen?

The always definitive Urban Dictionary sez:

Darn you, hidden UrbanDictionary page 2 link!