Nothing is really known about the presumed Zulian tribe. It was formerly implied by the Zulian Coins, found in Zul'Gurub at the first engagement of the Horde and Alliance. The other coins refer to tribes, but no other mention of the Zulian tribe can be found.
Battle for Azeroth
The animal species may have been named after the tribe like other beasts the tribes bred.
Nearly all other troll tribes with names in Zandali end with an -i or (rarely) an -ashi suffix. The unique "Zulian" construction could be related to anything denoted by the Zul prefix, including Zul'Gurub itself, where all evidence of the "tribe" is found.