An Etymological Dictionary of Astronomy and Astrophysics

1. Readily perceived by the eye or the understanding; evident; obvious; apparent; plain.
   

2. To make clear or evident to the eye or the understanding; show plainly (Dictionary.com).

Etymology (EN): M.E., from O.Fr. manifest “evident, palpable,” or from L. manifestus “plainly apprehensible, clear, apparent, evident;” “proved by direct evidence;” “caught in the act,” probably from manus “hand,” + -festus “struck;
(able to be) seized.”

Etymology (PE): From Torbat-Heydariye-yi nemusâr “evident, conspicuous, visible,” from nemu-, nemudan “to show, display”
from Mid.Pers. nimūdan, from ne- “down; into;” O.Pers./Av. ni- “down; below; into,” → ni-, + mu- (as in âz-mu-dan, â-mu-dan, far-mu-dan, pey-mu-dan, etc.); Av. mā(y)- “to measure,” → display, + -sâr a suffix of state, position, similarity.