1570s, "ruling; controlling; exerting power, authority, or influence," from French prédominant (14c.), from Medieval Latin *praedominantem (nominative praedominans), present participle of *praedominare, from Latin prae "before" (see pre-) + dominari "to rule, dominate, to govern," from dominus "lord, master," from domus "house" (from PIE root *dem- "house, household"). Weakened sense of "more frequent, prevalent" is from c. 1600. Related: Predominantly.
Predominant implies activity, and actual or figurative effort after leadership on the part of that which is predominated over: as, a predominant faction; a predominant opinion is one that seems to put down all others. [Century Dictionary]