The story
Uncertain. Originally attested as a criminal cant word for "burglar's tool-box" in 1881. In the 20th century a clutch of criminal slang meanings are mentioned, including "safe, strongbox". "Tripe and keister" had been the phrase for a conman's or a pitchman's display case on a tripod. A likely origin is the word Kiste, which means a box or case, in both German and Yiddish.
Etymology from Wiktionary, CC BY-SA 4.0.