Numen: the spirit or divine power presiding over a thing or place.
"the spirit of the place—its numen—was strong"
The literal meaning is simply "a nod", or more accurately, for it is a passive formation, "that which is produced by nodding", just as flamen is "that which is produced by blowing", i.e., a gust of wind.
It came to mean "the product or expression of power" — not, be it noted, power itself.
Numen (plural numina) is a Latin term for "divinity", "divine presence", or "divine will."
The Latin authors defined it as follows: Cicero writes of a "divine mind" (divina mens), a god "whose numen everything obeys," and a "divine power" (vis divina) "which pervades the lives of men."