chthonic (adj.)

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.

Proto-Indo-European root meaning "earth."

It forms all or part of: antichthon; autochthon; autochthonic; bonhomie; bridegroom; camomile; chameleon; chernozem; chthonic; exhume; homage; hombre; homicide; hominid; Homo sapiens; homunculus; human; humane; humble; humiliate; humility; humus; inhumation; inhume; nemo; ombre; omerta.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit ksam- "earth" (opposed to "sky"); Greek khthōn "the earth, solid surface of the earth," khamai "on the ground;" Latin humus "earth, soil," humilis "low;" Lithuanian žemė, Old Church Slavonic zemlja "earth;" Old Irish du, genitive don "place," earlier "earth."