statistical adj.

1770, "science dealing with data about the condition of a state or community" [Barnhart], from German Statistik, popularized and perhaps coined by German political scientist Gottfried Aschenwall (1719-1772) in his "Vorbereitung zur Staatswissenschaft" (1748), from Modern Latin statisticum (collegium) "(lecture course on) state affairs," from Italian statista "one skilled in statecraft," from Latin status "a station, position, place; order, arrangement, condition," figuratively "public order, community organization," noun of action from past participle stem of stare "to stand" from PIE root *sta- "to stand, make or be firm."

OED points out that "the context shows that [Aschenwall] did not regard the term as novel," but current use of it seems to trace to him. Sir John Sinclair is credited with introducing it in English use. Meaning "numerical data collected and classified" is from 1829; hence the study of any subject by means of extensive enumeration. Abbreviated form stats first recorded 1961.

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).