Where does “unconstancy” come from?

unconstancy (English) comes from English inconstancy, from English constancy, from Latin Constantia, from Latin cōnstāre.

unconstancy (English): Obsolete form of inconstancy; in Webster’s...

Definitions

Step	Language	Word	Meaning
1	English	inconstancy	Lack of constancy; lack of consistency in...
2	English	constancy	The quality of being constant; steadiness or...
3	Latin	Constantia	—
4	Latin	cōnstāre	—

unconstancy — Etymology, Origin & Word History | Etymology Explorer