Could the origin of "gangway" as an interjection be from Cantonese?
It appears that there is no evidence of a possible origin from Cantonese. Gangway has its roots in Old English gangweg "road, passage, thoroughfare”.
temporary passageway" to a ship, building under construction, etc., ultimately from Old English gangweg "road, passage, thoroughfare;" a compound of gang (n.) in its original sense "a going, journey, way, passage" and way (n.).
(Etymonline)