An Etymological Dictionary of Astronomy and Astrophysics

1. Having qualities appropriate to or usually associated with a man.
   

2. Of, relating to, or constituting the gender that ordinarily includes most words or grammatical forms referring to males (Merriam-Webster.com).

Etymology (EN): M.E. masculin, from O.Fr. masculin “of the male sex,” from L. masculinus “male, of masculine gender,” from masculus “male, masculine; worthy of a man,” diminutive of mas “male person, male,” of unknown origin.

Etymology (PE): Narin, from nar, → male.