(n.) the love a parent has for their children
The innate loving feeling that a parent has for their offspring is called philoprogenitiveness.
Ironically, as handsome as that word is, its own parentage isn’t quite so attractive. Philoprogenitiveness was coined in 1815 by Johann Spurzheim, one of the nineteenth century’s greatest proponents of phrenology.
Phrenology was the pseudoscience that connected the bumps on a person’s skull to their personality and mental traits. That connection has now long been discredited, of course, and phrenology’s later associations with the eugenics movement of the early 1900 has cast a long shadow over it and its early proponents. Nevertheless, it was in this questionable context that philoprogenitiveness was first coined in Spurzheim’s early explanation of all things phrenological, The Physiognomical System:
There is no single word which indicates the love of offspring. Hence I took two Greek roots. I am aware that the name is long, but I could not say philogenitiveness, because the name ought to indicate love of producing offspring. As however progeny means offspring, and philoprogeny love of offspring, and philoprogenitiveness the faculty of producing love of offspring, I have adopted that term.
Johann Spurzheim, The Physiognomical System of Drs Gall and Spurzheim (1815)
Spurzheim (and, moreover, the German physician and pioneer of phrenology, Franz Joseph Gall) believed that there was a distinct “organ of philoprogenitiveness” located in a noticeable “protuberance on the posterior part of the skulls of women.” Seemingly finding this prominence only on the skulls of women and children, Gall initially thought it must be the seat of “the greater irritability” he believed women and children to exhibit. (He was nothing if not a product of his time.) Happily, he later reconsidered his approach, and decided instead this bony lump must be connected to childbirth, childhood, and the parental love that connects children to their birth parent—hence Spurzheim’s invented name for it.
From its early connections with the madness of phrenology, by the 1900s philoprogenitiveness was being used in a looser sense to describe the reciprocal feeling between parents and children. And as phrenology continued to drift into obscurity, it was this meaning that survived—albeit on the fringes of our vocabularies.