"student of, or dealer in, herbs," 1590s, from herbal + -ist. Earlier such a person might have been called herber (early 13c. as a surname), herbarian (1570s), herbarist, herb-man, herbary (1540s). Fem. formation herb-wife is attested from 1580s.
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.
<a href="https://www.etymonline.com/word/herbalist">Etymology of herbalist by etymonline</a>
Harper, D. (n.d.). Etymology of herbalist. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/herbalist