c.1300, "Church father," from O.Fr. doctour, from M.L. doctor "religious teacher, adviser, scholar," in classical L. "teacher," agent noun from docere "to show, teach, cause to know," originally "make to appear right," causative of decere "be seemly, fitting" (see decent). Meaning "holder of highest degree in university" is first found late 14c.; as is that of "medical professional" (replacing native leech (2)), though this was not common till late 16c. The transitional stage is exemplified in Chaucer’s Doctor of phesike (Latin physica came to be used extensively in M.L. for medicina). Similar usage of the equivalent of doctor is colloquial in most European languages: cf. It. dottore, Fr. docteur, Ger. doktor, Lith. daktaras, though these are typically not the main word in those languages for a medical healer. For similar evolution, cf. Skt. vaidya- “medical doctor,” lit. “one versed in science.” Ger. Arzt, Du. arts are from L.L. archiater, from Gk. arkhiatros “chief healer,” hence “court physician.” Fr. médecien is a back formation from médicine, replacing O.Fr. miege, from L. medicus.

see: therapeutic healer