hap vs occur

hap is a noun but occur is not a noun.

Word	Noun	Adjective	Verb	Adverb
hap	Yes	No	Yes	No
occur	No	No	Yes	No

As verbs, hap and occur are synonyms defined as:

Other synonyms of hap include come about, fall out, go on, happen, pass, pass off, take place.

hap (noun)	occur (noun)
an accidental happening

hap (verb)	occur (verb)
come to pass	come to pass
	come to one's mind; suggest itself
	to be found to exist