This term was used on the internet as an onomatopoeia of eating. Often pictures of huge gaping mouths (not to be confused with shoop da whoop) would be eating
something with the caption "OM NOM NOM NOM".
Later, some teenage douchbag emo
freak turds took the Nom and made it a term for someone who is BEWTEHLISHUS ^.^ ...
And now to the insult of the entire internets, this has been changed into a shitty yoghurt and in their TV advert, loads of
people are going "HAHAHANOM" and other ridiculous sound effects residing with nom, ruining the entire word and enabling it to enter the world of technophobic oldies.
Cute
people who also like to jump around town in tiny wide brimmed skirts and pink hair shouting "DESU!" also have changed this word to "Nahm"
This is also a term for voreaphiliacs and cannibals(unsurprisingly).