late 14c., "ancient Roman settlement outside Italy," from Latin colonia "settled land, farm, landed estate," from colonus "husbandman, tenant farmer, settler in new land," from colere "to cultivate, to till; to inhabit; to frequent, practice, respect; tend, guard," from PIE root *kwel- (1) "revolve, move round; sojourn, dwell" (source also of Latin -cola "inhabitant"). Also used by the Romans to translate Greek apoikia "people from home."
In reference to modern situations, "company or body of people who migrate from their native country to cultivate and inhabit a new place while remaining subject to the mother country," attested from 1540s. Meaning "a country or district colonized" is by 1610s.
word-forming element meaning "one who does or makes," also used to indicate adherence to a certain doctrine or custom, from French -iste and directly from Latin -ista (source also of Spanish, Portuguese, Italian -ista), from Greek agent-noun ending -istes, which is from -is-, ending of the stem of verbs in -izein, + agential suffix -tes.
Variant -ister (as in chorister, barrister) is from Old French -istre, on false analogy of ministre. Variant -ista is from Spanish, popularized in American English 1970s by names of Latin-American revolutionary movements.