Origin and history of practitioner

"an inhabitant or member of the community of a parish," mid-15c., with -er (1), from earlier parishen "parishioner" (c. 1200), from Old French paroissien, parochien, from paroisse (see parish). The doublet form parochian was obsolete by 1700.

early 15c., practise, "practical aspect or application," originally especially of medicine but also alchemy, education, etc.; from Old French pratiser, from Medieval Latin practicare (see practice (v.)). It largely displaced the older word, practic, which survived in parallel into 19c. From early 15c. it began to be assimilated in spelling to nouns in -ice.

Sense of "habit, frequent or customary performance" is from c. 1500. Meaning "exercise for instruction or discipline" is from 1520s. Sense of "action, the process of accomplishing or carrying out" (opposed to speculation or theory) is from 1530s. The meaning "regular pursuit of some employment or business" is from 1570s. In 16c.-17c. it also was used in an evil sense, "conspiracy, a scheme."

Practice is sometimes erroneously used for experience, which is a much broader word. Practice is the repetition of an act : as, to become a skilled marksman by practice. Experience is, by derivation, a going clear through, and may mean action, but much oftener views the person as acted upon, taught, disciplined, by what befalls him. [Century Dictionary]

"a practitioner; one who practices (as distinguished from one who theorizes," originally also practitian, c. 1500, from Old French practicien (Modern French praticien), from Late Latin practicus "fit for action," (see practice (v.)). An earlier word was practisour (late 14c.).