ataxic (adj.)

often Englished as ataxy, 1660s in pathology, "irregularity of bodily functions," medical Latin, from Greek ataxia, abstract noun from a- "not, without" (see a- (3)) + taxis "arrangement, order," from stem of tassein "to arrange" (see tactics). It was used earlier in English in a sense of "confusion, disorder" (1610s).

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.