1620s, of drugs, "inducing sleep," from French hypnotique (16c.) "inclined to sleep, soporific," from Late Latin hypnoticus, from Greek hypnotikos "inclined to sleep, putting to sleep, sleepy," from hypnoun "put to sleep," from hypnos "sleep" (from PIE root *swep- "to sleep"). Modern sense of "pertaining to an induced trance" first recorded in English 1843, along with hypnotize, hypnotism, hypnotist, in the works of hypnotism pioneer Dr. James Braid. Related: Hypnotical; hypnotically.
-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.