jumping bean, n. — Green’s Dictionary of Slang

jumping bean n.

[play on SE Mexican jumping bean, seed pods that have been inhabited by the larva of a small moth (Cydia deshaisiana); they ‘jump’ when heated]

(US) derog. term for a Mexican.

2012

H. Acosta ‘Doing the Job’ in ThugLit Dec. [ebook] Fucking Oscar, I should have known. Damn jumping bean had a hard-on for me ever since I got here.