Conniption fit

What is the meaning and origin of " kanipshin fit ".

From dictionary.com:
con·nip·tion
n. Informal
A fit of violent emotion, such as anger or panic. Also called conniption fit.

[Origin unknown.]

Which is more serious a conniption fit or a hissy fit?

To my mind (other minds may differ), the two are similar, and a conniption fit is more serious. Hissy fits are more showy and superficial. We call an outburst a hissy fit if it's way out of proportion to what occasioned it.