Where does “Ἠλέκτρα” come from?

Ἠλέκτρα (Ancient Greek) comes from Ancient Greek -ᾱ, from Proto-Indo-European -éh₂.

Ancestry of “Ἠλέκτρα”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	-ᾱ	nominal suffix
2	Proto-Indo-European	-éh₂	—