-ical

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.

1660s, "of or belonging to history," probably a back-formation from historical, perhaps influenced by French historique. Meaning "what is noted or celebrated in history" is from 1794.

Though both historic and historical have been used in both senses by respected authors, now the tendency is to reserve historic for what is noted or celebrated in history; historical for what deals with history. The earliest adjective form of the word in English was historial (late 14c., from Late Latin historialis), which meant "belonging to history; dealing with history; literal, factual, authentic," and also "of historical importance" (early 15c.).