empiricist n.

"pertaining to or derived from experience or experiments," c. 1600, from Latin empiricus (n.) "a physician guided by experience," from Greek empeirikos "experienced," from empeiria "experience; mere experience or practice without knowledge," especially in medicine, from empeiros "experienced (in a thing), proven by use," from assimilated form of en "in" (see en- (2)) + peira "trial, experiment," from PIE *per-ya-, suffixed form of root *per- (3) "to try, risk." Originally a school of ancient physicians who based their practice on experience rather than theory. Earlier in English as a noun (1540s) in reference to the sect, and earliest (1520s) in a sense "quack doctor" which was in frequent use 16c.-19c.

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.