Green’s Dictionary of Slang

come over v.1

[ext. use of SE come over, to prevail]

[17C+] to trick, to cheat; to get the better of.

SE in slang uses

In phrases

come over on a whelk-stall (v.) [? the flashy dress preferred by whelk-sellers]

[late 19C–1900s] (costermonger) to be very flashily dressed.