An Etymological Dictionary of Astronomy and Astrophysics

1. A person with the ability or power to use, control, or dispose of something.
   

2. An employer of workers or servants.
   

3. The male head of a household (Dictionary.com).

Etymology (EN): M.E. maistre, maister, from O.E. magister, from L. magister “chief, head, director, teacher,” ultimately from PIE root *meg- “great,” cf. Pers. meh-, as below.

Etymology (PE): (Aftari) Mastar “elder; larger,” (Dari Kermân) mastar “leader, guide,” variants (Aftari, Tafreši) mester “elder; great,” massar “large, great, high,” from (Nâini, Sangesari, Dari Yazd, Kermâni) mas “great, large,” variant of meh “great, large, principal,” cognate with L. magister “chief, head, director, teacher;” → Big Bang, + comparative suffix -tar.