The first occurrence.
And YHVH God caused a deep sleep to fall upon Adam, and he slept: and He took one of his ribs, and closed up that flesh instead. Gen 2:21
The primitive root.
Strong’s H5307 נפל naphal, a primitive root meaning, “to fall, to cause to fall, to fall upon.” The 3-letter root is nun + pey + lamed.
nun ן, נ = the seed, thus continue, heir, son
pey ף, פ = the mouth, thus open, blow, scatter, edge
lamed ל = the shepherd’s staff, thus teach, yoke, to, bind
The story: The son (nun) of the judge, i.e. the mouth (pey) speaking with authority (lamed), or the mouth which pronounces judgment.
The definition appears to refer to its use as a root of Nephilim,
1 And it came to pass, when men began to multiply on the face of the earth, and daughters were born to them, 2 that the sons of God (bene-ha’elohiym) saw that the daughters of men were fair; and they took wives for themselves, whoever they chose. 3 And YHVH said: My Spirit shall not abide in man forever, for he is flesh; therefore his days shall be one hundred and twenty years. 4 The giants (nephilim) were in the earth in those days, and also after that, when the sons of God (bene-ha’elohiym) came in to the daughters of men, and they bore children to them; the same were the mighty men that were of old, the men of renown. Gen 6:1-4
where sons of rulers or sons of judges (bene-ha’elohiym) begot children by the daughters of men – which they had attacked or fallen upon, taking them by force – who became the mighty men of renown, the nephilim.