The following slang, euphemisms, and terms are for the letters X, Y, and Z and are primarily taken from Francis Grose’s Classical Dictionary of the Vulgar Tongue published in 1811.
XANTIPPE was the name of Socrates wife and she was described by Plato as a devoted wife and mother. However, over time writers begin to describe her as bad-tempered and shrewish, until eventually the word became associated with a shrew or scolding wife.
XOWYNE meant to shove.
XYSTER was a surgeon’s instrument used to scrape bones, similar to a rasp or a file.
YACK was used to refer to a watch.
YANKEY or YANKEY DOODLE was the appellation given to Americans by the British. The term “yankey” is supposedly a derivation of “nankey,” which was applied to Oliver Cromwell, and “doodle” was an old English word that meant a simpleton or trifling fellow. The appellation apparently become popular before the Revolutionary War when the British changed Yankey to Yankee and began singing the song “Yankee Doodle” to the disorganized rag-tag colonists just before the Battle of Lexington and Concord.
YARNHOSE was exactly that, a hose made of yarn.
YARMOUTH COACH was a term used in ridicule because a YARMOUTH COACH was not a coach at all. Rather it was a low, two-wheeled cart drawn by a single horse.
YARMOUTH PIE was “a pye made of herrings highly spiced, which the city of Norwich is by charter bound to present annually to the king.”
A YEA AND NAY MAN was a simple fellow that answered either “yes” or “no.”
If you looked YELLOW it was said you were jealous.
YELLOW BELLY referred to the natives of Fens in Lincolnshire County, a county that was also linked to a 14-year-old boy who was killed by the London Burkers, John Bishop and Thomas Williams. YELLOW BELLY also was an allusion to the eels that people caught there.
YELLOW BOYS was another name for guineas.
YELLOW JACK referred to yellow fever.
TO YELP meant to cry out, and a YELPER was the nickname give to the town crier.
YERK meant to throw out or to move with a spring in your step.
YEST was a contraction of yesterday.
If you were married you were YOKED.
YOKEL was an insulting name, similar to country bumpkin, and applied by a city person when speaking of someone from the countryside.
A YORKSHIRE TYKE was a Yorkshire clown and one of the most infamous persons from Yorkshire was Mary Bateman, known as the “Yorkshire Witch” or the “Witch of Leeds.”
ZAD referred to a crooked or deformed person, because supposedly the person was similar to the letter Z with its zig zags.
ZANY referred to a court jester, a buffoon, or a mountebank.
ZEDLAND referred to the western countries where the letter Z was substituted for the letter S. For instance, according to Grose, “zee for see, zun for sun.”
A ZOOGRAPHER was someone who described animals, but a ZOOPHILIST was a lover of everything living.
-  Egan, P., Grose’s Classical Dictionary of the Vulgar Tongue, 1823.
-  Grose, F., Dictionary of Buckish Slang, University Wit, and Pickpocket Eloquence, 1811.