also gynaecology, "science of women's health and of the diseases peculiar to women," 1847, from French gynécologie, from Latinized form of Greek gynaiko-, combining form of gynē "woman, female," from PIE root *gwen- "woman." Second element is from French -logie "study of," from Greek (see -logy). Another word for it was gyniatrics.
-ist
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.