The first occurrence.
And God saw the light, that it was good: and God divided between the light and between the darkness. Gen 1:4
The primitive root.
bet ב = the house, thus house, household, family, in, within
yud י = the closed hand, thus work, throw, worship
nun נ, ן = the seed, thus continue, heir, son
In the era of the patriarchs, from the Ancient Hebrew Lexicon:
The tent was usually divided into two parts, one for the females and the other for the male[s]. The wall makes a distinction between the two sides.
The story: The house or tent (bet) was closed off (yud) according to the genders determined by the seed (nun). “To understand” is the ability to discern between two things.