yarbles

Yarbles was coined by Anthony Burgess in 1962, when he introduced it as slang for "testicles" within the invented dialect Nadsat of his dystopian novel A Clockwork Orange. The word is generally understood to be a derivation from Russian яблоко (jabloko, “apple”), owing to the variant form "yarblockos" used within the same novel. Jabloko does not have the equivalent vulgar connotation among Russian speakers, although яйца (jajca, literally “eggs”) does, which may have influenced the word. Green's Dictionary of Slang posits an possible alternate origin as yarb + balls: a combination of the antiquated, sometimes-derogatory English dialect word "yarb" with the vulgar colloquialism "balls". Others have suggested a connection to marbles via the methods of English rhyming slang.

来源：wiktionary