An Etymological Dictionary of Astronomy and Astrophysics

1. Logic: Relating to or involving deductive reasoning from a general principle to the expected facts or effects (dictionary.com).
   

2. Logic: Known to be true independently of or in advance of experience of the subject matter; requiring no evidence for its validation or support (dictionary.com). → a posteriori.

Etymology (EN): L., literally “from what comes first,” from priori, ablative of prior
“former, previous, first,” → per-.

Etymology (PE): Partom “the first,” Dehxodâ: fardom; Mid.Pers. fradom, fratom, pratom; O.Pers. fratama-; Av. fratəma- (Skt. prathama- “earliest, initial, first”) superlative of fra- “before, forward, forth,” cognate with Gk. and L. → pro-.