1620s, "to cast as seed," from inseminatus, past participle of Latin inseminare "to sow, implant," from in- "in" (from PIE root *en "in") + semen (genitive semenis) "seed" (from PIE root *sē- "to sow"). Meaning "to impregnate with semen" is attested from 1897.
It has seemed necessary, therefore, to make a distinction between the introduction of seminal fluid into the female generative organs of animals and the subsequent possible fertilisation of their ova, and for that purpose I have used the word "inseminate," which can thus be applied to animals in precisely the same way as the word "pollenate" is applied by some botanists to denote the placing of pollen on the stigma of a plant. [Walter Heape, "The artificial Insemination of Mammals," "Proceedings of the Royal Society of London," vol. lxi, 1897]
Related: Inseminated; inseminating.