Yankey, or Yankey doodle.  A booby, or country
  lout:  a name given to the New England men in North
  America.  A general appellation for an American.

Yarmouth capon.  A red herring:  Yarmouth is a
  famous place for curing herrings.

Yarmouth coach.  A kind of low two-wheeled cart
  drawn by one horse, not much unlike an Irish car.

Yarmouth pye.  A pye made of herrings highly spiced,
  which the city of Norwich is by charter bound to present
  annually to the king.

YARUM.  Milk.  Cant.

Yea and Nay man.  A quaker, a simple fellow, one who
  can only answer yes, or no.

Yellow.  To look yellow; to be jealous.  I happened to
  call on Mr. Green, who was out:  on coming home, and
  finding me with his wife, he began to look confounded
  blue, and was, I thought, a little yellow.

Yellow belly.  A native of the Fens of Licoinshire; an
  allusion to the eels caught there.

Yellow boys.  Guineas.

To yelp.  To cry out.  Yelper; a town cryer, also one
  apt to make great complaints on trifling occasions.

YEST. A contraction of yesterday.

YOKED. Married.  A yoke; the quantum of labour performed
  at one spell by husbandmen, the day’s work being
  divided in summer into three yokes.  Kentish term.

Yorkshire tyke.  A Yorkshire clown.  To come Yorkshire
  over any one; to cheat him.

Young one.  A familiar expression of contempt for another’s
  ignorance, as “ah!  I see you’re a young one.”  How
  d’ye do, young one?

To yowl.  To cry aloud, or howl.

ZAD.  Crooked like the letter Z. He is a mere zad, or
  perhaps zed; a description of a very crooked or deformed
  person.

Zany.  The jester, jack pudding, or merry andrew, to a
  mountebank.

ZEDLAND.  Great part of the west country, where the
  letter Z is substituted for S; as zee for see, zun for sun,