TO MAKE OFFSPRING

When the word prolific was first used in the English language by historian Thomas May, it was spelled prolifique and had to do with fertility and producing lots of offspring. Later on, that expanded to include more figurative definitions, after which usage over time remained relatively constant. Prolifique is glaringly French, crossing the channel in the 1630s and taken from Latin prolificus in the 1500s. The Latin word combines two others: proles, meaning "offspring" and facere, "to make" (so to be prolific is to make offspring). Proles can be traced back to two Proto-Indo-European roots, pro (meaning "forth") and al ("to grow"), and I've covered facere on multiple occasions; it derives from PIE dhe, "to put". So much development over time - I guess you could say this was quite a prolific etymology.