I already discussed the origins of human, man, and woman (in fact, it was a year ago last Saturday), so I might as well learn about “people”.
People showed up in English in the late thirteenth centurywith basically the same definition, although the secondary definition of people (as in, an ethnic group) didn’t for more than a century. It had already showed up in Anglo Frenchas people (yes, it’s so hard to imagine) and in Old Frenchas peupel, in all cases meaning humans in a general sense.
It’s worth noting that English already had a word for people—folk—that was so cruelly displaced by a younger, cooler word. But if you’ve spent any amount of time reading these etymology posts, you’d realize that pretty much everything has Latin progenitors and the descendants of Proto-Germanicare no exception. Old French’s peupel was taken from the classical Latin populus.
That’s the origin for quite a few English words. Popular, population, and public are all cousins of people. The Latin publicus comes from the above mentioned populus, and popular comes from popularis, which means “belonging to the people”. Population comes from the Late Latin populationem, “a multitude”.
TL;DR: People is popular.