1912, from Modern Latin, literally "a splitting of the mind," from German Schizophrenie, coined in 1910 by Swiss psychiatrist Eugen Bleuler (1857-1939), from Greek skhizein "to split" (from PIE root *skei- "to cut, split") + phrēn (genitive phrenos) "heart, mind" (hence phrenes "wits, sanity"); see phreno-.
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.