onomancy vs foretelling

onomancy and foretelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
onomancy	Yes	No	No	No
foretelling	Yes	No	No	No

As nouns, foretelling is a hypernym of onomancy; that is, foretelling is a word with a broader meaning than onomancy:

onomancy: divination by the letters of a name
foretelling: the art or gift of prophecy (or the pretense of prophecy) by supernatural means

Other hypernyms of onomancy include divination, fortune telling, soothsaying.

onomancy (noun)	foretelling (noun)
divination by the letters of a name	the art or gift of prophecy (or the pretense of prophecy) by supernatural means
	a statement made about the future