sickliness vs frailty

sickliness and frailty both are nouns.

Word	Noun	Adjective	Verb	Adverb
sickliness	Yes	No	No	No
frailty	Yes	No	No	No

As nouns, frailty is a hypernym of sickliness; that is, frailty is a word with a broader meaning than sickliness:

sickliness: The state or characteristic of weakness, incapacity, or physical distress due to poor health, especially of a chronic nature.
frailty: the state of being weak in health or body (especially from old age)

Other hypernyms of sickliness include debility, feebleness, frailness, infirmity, valetudinarianism.

sickliness (noun)	frailty (noun)
The state or characteristic of weakness, incapacity, or physical distress due to poor health, especially of a chronic nature.	moral weakness
	the state of being weak in health or body (especially from old age)