The OED included hissy fit in their entry for hissy, writing: hissy fit n. chiefly U.S. a fit of temper, an angry outburst, a tantrum. 1967 in Dict. Amer. Regional Eng. (1991) II. 1021/2 Pitched a hissy-fit. 1978 A. Maupin Tales of City 5 When I told my mom I was moving to San Francisco, she had an absolute hissy-fit! 1981 F. Flagg Coming Attractions 21 Momma always looks like she is on the ...
etymology - What is the origin of "hissy fit"? - English Language ...
Throw a fit is not an offensive term. It is not directly associated with epileptic fits--a hissy fit or snit fit or shit fit...that is to say, a tantrum. Thus, it might be an unkind thing to say someone did, but the language itself is not ableist or otherwise distasteful. You bring up throw a tantrum. It is no more childish than throw a fit. Both refer to the exact same behavior. Depending on ...
I don't think it's exactly an "old medical term" - more of a rather quaint AmE slang term for tantrum, about on a par with "hissy fit". OED lists it as US vulgar, first recorded 1833.
Is 'throw a fit' offensive? - English Language & Usage Stack Exchange
The OED notes of psithurism, "Obsolete. Forms: α. psithurisma. β. psithurism. This word belongs in Frequency Band 1. Band 1 contains extremely rare words unlikely ever to appear in modern text. These may be obscure technical terms or terms restricted to occasional historical use, e.g. abaptiston, abaxile, grithbreach, gurhofite, zarnich, zeagonite.* The only 4 examples are taken from dates ...