clonus

borrowed from New Latin, borrowed from Greek klónos "chaotic throng, press (as of warriors in battle), physiological commotion (in the bowels)," perhaps from *kl-, zero grade of the Indo-European verbal base *kelh₁- "set in motion" + -onos, noun suffix — more at accelerate

Note: The Indo-European etymon *kelh₁- "set in motion" is based on I. Seržant, "Die idg. Wurzeln *kel₁- 'etw. bewegen' und *kelh₃- 'sich erheben'," Indogermanische Forschungen, Band 113 (2008), pp. 59-75. This etymology of klónos is supported by P. Chantraine (Dictionnaire étymologique de la langue grecque) and Lexikon der indogermanische Verben (2nd edition, p. 348), though the latter operates with a root *kel- "drive, urge" (antreiben) and actually takes klónos as evidence that *kel- did not have a following laryngeal. R. Beekes (Greek Etymological Dictionary), on the other hand, is skeptical of any connection with such a root. The only exactly parallel derivative appears to be thrónos "seat, throne entry 1," the etymology of which is also doubtful.