sociologist (n.)

the science of social phenomena, 1842, from French sociologie, a hybrid coined 1830 by French philosopher Isidore Auguste Comte (1798-1857), from Latin socius "associate" (see social (adj.)) + Greek-derived suffix -logie (see -logy).

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.