firing vs ending

firing and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
firing	Yes	No	No	No
ending	Yes	No	No	No

As nouns, ending is a hypernym of firing; that is, ending is a word with a broader meaning than firing:

firing: the termination of someone's employment (leaving them free to depart)
ending: the act of ending something

Other hypernyms of firing include conclusion, termination.

firing (noun)	ending (noun)
the act of setting something on fire	the act of ending something
the termination of someone's employment (leaving them free to depart)	the end of a word (a suffix or inflectional ending or final morpheme)
the act of discharging a gun	the last section of a communication
the act of firing weapons or artillery at an enemy	event whose occurrence ends something
	the point in time at which something ends