The first occurrence.
And God called the light Day, and the darkness He called Night. And there was evening and there was morning, one day. Gen 1:5
The primitive root.
aleph א = the ox head, thus strength, power, leader
chet ח = the wall, thus outside, divide, half
dalet ד = the door, thus enter, move, hang
The parable being told: To strongly (aleph) fence (chet) the door (dalet). When a man and his wife are one, the door is strongly fenced so that exiting (either the house or the relationship) is not an option.