"He's interested in anything he can sell."
-- Tina Goldstein (WFT)
Gnarlak was a Goblin living in 1920s New York City. He is something of an underworld figure who, among other things, traded in magical creatures. Gnarlak had been an informant for Tina Goldstein and she took Newt to meet him in the Blind Pig while they were looking for a missing demiguise. He wasn’t swayed by Galleons or a frozen Ashwinder egg, but he definitely wanted to get his hands on a Bowtruckle (WFT).
gnarl = a knobby bump on a tree trunk or branch
gnar or gnarr: Eng "to snarl or growl"