earthing vs fastening

earthing and fastening both are nouns.

Word	Noun	Adjective	Verb	Adverb
earthing	Yes	No	No	No
fastening	Yes	No	No	No

As nouns, fastening is a hypernym of earthing; that is, fastening is a word with a broader meaning than earthing:

Other hypernyms of earthing include attachment.

earthing (noun)	fastening (noun)
fastening electrical equipment to earth	the act of fastening things together
	restraint that attaches to something or holds something in place