Green’s Dictionary of Slang

newt n.

[SE neuter or neutral]

(US campus) a stupid, unsophisticated or socially inadequate person.

[Aus](con. 1830s–60s) ‘Miles Franklin’ All That Swagger 150: If ye’r father is such a newt to be put upon to that extint.
[US]P. Munro Sl. U. 137: Adrian can’t get girls ’cause he’s such a newt.