I viewed the thread about conniption dido - which I'd never heard before. But was wondering what true meaning of conniption was? I always figured it was an old medical term for seizure or something.
The meaning of "conniption" is "a fit of rage or hysterics."
The etymology of "conniption" is unclear. Many sources note that the first appearance of this word is in 1833 but no one has yet found the source of the word. There is a good, short review of this subject here:
with a few more interesting details.