Meaning

noun a display of bad temper

noun a sudden uncontrollable attack

noun the manner in which something fits

originPossibly from Middle English fit (“an adversary of equal power”), of uncertain further origin. The original sense appears to have been "to marshal or deploy troops", which shifted to "to suit (troops to a certain location" > "suitable", and may be further related to Icelandic fitja (“to web, knit, cast on”).

Etymology from Wiktionary, CC BY-SA 3.0