Mr Hotten derives it from the Latin _Vocare_! I do not know the origin of WELCHER, a betting cheat, but it is worthy of remark that in old Gipsy a _Walshdo_ or Welsher meant a Frenchman (from the German Walsch) or any foreigner of the Latin races.
YACK, a watch, probably received its name from the Gipsy _Yak_ an eye, in the old times when watches were called bull's eyes.
LUSHY, to be tipsy, and LUSH, are attributed for their origin to the name of Lushington, a once well-known London brewer, but when we find _Losho_ and _Loshano_ in a Gipsy dialect, meaning jolly, from such a Sanskrit root as _Lush_; as Paspati derives it, there seems to be some ground for supposing the words to be purely Rommany.

Dr Johnson said of lush that it was "opposite to pale," and this curiously enough shows its first source, whether as a "slang" word or as indicative of colour, since one of its early Sanskrit meanings is _light_ or _radiance_.

This identity of the so regarded vulgar and the refined, continually confronts us in studying Rommany.
"To make a MULL of anything," meaning thereby to spoil or confuse it, if it be derived, as is said, from the Gipsy, must have come from _Mullo_ meaning _dead_, and the Sanskrit _Mara_.

There is, however, no such Gipsy word as mull, in the sense of entangling or spoiling.
PROSS is a theatrical slang word, meaning to instruct and train a tyro.
As there are several stage words of manifest Gipsy origin, I am inclined to derive this from the old Gipsy _Priss_, to read.

In English Gipsy _Prasser_ or _Pross_ means to ridicule or scorn.