late 14c., "observation as the source of knowledge; actual observation; an event which has affected one," from Old French esperience "experiment, proof, experience" (13c.), from Latin experientia "a trial, proof, experiment; knowledge gained by repeated trials," from experientem (nominative experiens) "experienced, enterprising, active, industrious," present participle of experiri "to try, test," from ex "out of" (see ex-) + peritus "experienced, tested," from PIE *per-yo-, suffixed form of root *per- (3) "to try, risk." Meaning "state of having done something and gotten handy at it" is from late 15c.

also reexperience, "experience again or anew," 1789, from re- "back, again" + experience (v.). Related: Re-experienced; re-experiencing.

"relating to or having experience, derived from experience, empirical," 1640s (implied in experientially), from Latin experientia "knowledge gained by testing or trials" (see experience (n.)) + -al (1).

Proto-Indo-European root meaning "to try, risk," an extended sense from root *per- (1) "forward," via the notion of "to lead across, press forward."

It forms all or part of: empiric; empirical; experience; experiment; expert; fear; parlous; peril; perilous; pirate.

It is the hypothetical source of/evidence for its existence is provided by: Latin experiri "to try," periculum "trial, risk, danger;" Greek peira "trial, attempt, experience," empeiros "experienced;" Old Irish aire "vigilance;" Old English fær "calamity, sudden danger, peril, sudden attack," German Gefahr "danger," Gothic ferja "watcher.

1560s, originally in medicine, "pertaining to or derived from experience or experiments," 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." With -al (1). In a general sense of "guided by mere experience" from 1757. Related: Empirically (1640s as "by means of observation and experiment").

"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.