An Etymological Dictionary of Astronomy and Astrophysics

1. A teacher who instructs students without institutional connection.
   

2. A teacher of a rank below instructor in some US universities.

Etymology (EN): From tutor, M.E., from O.Fr. tutour “guardian, private teacher,” from L. tutor “protector, watcher,” from tutus, variant p.p. of tueri “to watch over,” of unknown origin.

Etymology (PE): Âmuxtâr, literally “teacher,” from âmuxtan, → teach, + -âr agent noun suffix (such as xaridâr).