gyp · noun, verb1
Perhaps from the term gypsy (“Roma”), due to a stereotype of the Roma as swindlers. Compare jew (“defraud”), from Jew, and welsh (“swindle by defaulting on a debt”), from Welsh. Could also be derived from dupe, with the same pattern (yod coalescence) as idiot becomes eejit in Scottish English.
gyp · noun2
Perhaps the same as Etymology 1. An earlier theory derived the term from Ancient Greek γύψ (gúps, “vulture”) (/ɡýps/; compare Greek γύπας (gýpas) /ˈʝi.pas/), "in reference to thievish habits of the servants" (and then derived Etymology 1 thence), but this does not explain the pronunciation.
gyp · noun3
Shortening.
gyp · noun4
Perhaps from gee up.
Etymology from Wiktionary, CC BY-SA 4.0.