ataractic (adj.)

often Englished as ataraxy, c. 1600, "calmness, impassivity," a term used by stoics and skeptics, from Modern Latin, from Greek ataraxia "impassiveness," from a- "not, without" (see a- (3)) + tarassein (Attic tarattein) "to disturb, confuse," from PIE root *dhrehgh- "to confuse." It seems to have been disused; when ataraxia appeared in print in English in 1858 it was regarded as a neologism.

Middle English -ik, -ick, word-forming element making adjectives, "having to do with, having the nature of, being, made of, caused by, similar to," from French -ique and directly from Latin -icus or from cognate Greek -ikos "in the manner of; pertaining to." From PIE adjective suffix *-(i)ko, which also yielded Slavic -isku, adjectival suffix indicating origin, the source of the -sky (Russian -skii) in many surnames. In chemistry, indicating a higher valence than names in -ous (first in benzoic, 1791).

In Middle English and after often spelled -ick, -ike, -ique. Variant forms in -ick (critick, ethick) were common in early Modern English and survived in English dictionaries into early 19c. This spelling was supported by Johnson but opposed by Webster, who prevailed.