show-off vs swellhead

show-off and swellhead both are nouns.

Word	Noun	Adjective	Verb	Adverb
show-off	Yes	No	No	No
swellhead	Yes	No	No	No

As nouns, swellhead is a hypernym of show-off; that is, swellhead is a word with a broader meaning than show-off:

show-off: someone who deliberately behaves in such a way as to attract attention
swellhead: a conceited and self-centered person

Other hypernyms of show-off include egoist, egotist.

show-off (noun)	swellhead (noun)
someone who deliberately behaves in such a way as to attract attention	a conceited and self-centered person