An Etymological Dictionary of Astronomy and Astrophysics

1. A teacher of the highest academic rank in a college or university.
   

2. An instructor in some art or skilled sport, such as a professor of singing.

Etymology (EN): M.E. from L. professor “one who has taken the vows of a religious order,” agent noun from profitieri “declare openly,” from → pro- “forth” + fateri “to acknowledge, confess.”

Etymology (PE): Ostâd “professor; master; artisan,” from Mid.Pers. ôstât, from Av.
*aibi-stāta-, *auui-stāta- literally “standing on,” i.e. “appointed; agent; head,” from aibi-/auui- “upon, toward, against” (O.Pers. abiy-; cf. Skt. abhi-; Gk. amphi-) + stā- “to stand” (→ opposition).