convulsion (kon-VUHL-shuhn) - n., an intense, involuntary contraction of muscles; an uncontrolled fit (as of laughter), a paroxysm; a violent upheaval, disturbance, or agitation, esp. a social one.
The meaning, when it introduced around 1547, was a cramp or spasm, which makes sense given the prefix con-, a variant of com- in front of some consonants (related to cum, with), means together -- so a sudden pulling together, which intensified is a paroxysm.
Earthquakes and other convulsions of nature shake Earth on a regular basis.
---L.
