gyp

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.

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.

Shortening.

Perhaps from gee up.