Green’s Dictionary of Slang

snit n.

[? echoic; coined by US writer/diplomat Clare Booth Luce (1903–87)]

1. [1930s; 1960s+] (orig. US, also snit-fit) an outbreak of temper, generally a children’s term; thus snitty adj.

2. [1960s] an aloof individual.

In derivatives

snittiness (n.)

[2000s] ill temper, verbal unpleasantness.