Meaning

noun large important food fish of Australia; almost indistinguishable from the maigre

noun large dark grouper with a thick head and rough scales

originFor Australian fish such as Argyrosomus species, jewel and fish; see jewie. For New World species, from 17th century Jamaican English and refers to the kosher status of the Atlantic goliath grouper from at least 1697 onwards, likely as a derogatory term despite Jamaican Jews being treated better in the rule of the English than the Spanish rule.

Etymology from Wiktionary, CC BY-SA 3.0