fastness vs swiftness

fastness and swiftness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fastness	Yes	No	No	No
swiftness	Yes	No	No	No

As nouns, fastness and swiftness are synonyms defined as:

fastness and swiftness: a rate (usually rapid) at which something happens

Other synonyms of fastness include speed.

fastness (noun)	swiftness (noun)
a strongly fortified defensive structure	a rate (usually rapid) at which something happens
a rate (usually rapid) at which something happens
the quality of being fixed in place as by some firm attachment