fastening vs earthing

fastening and earthing both are nouns.

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

As nouns, earthing is a hyponym of fastening; that is, earthing is a word with a more specific, narrower meaning than fastening:

Other hyponyms of fastening include bonding, soldering, doweling, grounding, linkage, ligature, tying, welding, fixation.

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