Where does “Ахерон” come from?

Ахерон (Russian) comes from Latin Acheron, from Ancient Greek Ἀχέρων, from Ancient Greek ἄχος, from Proto-Indo-European h₂égʰos, from Proto-Indo-European h₂egʰ- — to be upset, afraid.

Ancestry of “Ахерон”, step by step

Step	Language	Word	Meaning
1	Latin	Acheron	Acheron, a river in the underworld
2	Ancient Greek	Ἀχέρων	lamentation
3	Ancient Greek	ἄχος	distress; pain, ache
4	Proto-Indo-European	h₂égʰos	distress
5	Proto-Indo-European	h₂egʰ-	to be upset, afraid

Every word from Proto-Indo-European h₂egʰ- →Every word from Proto-Indo-European h₂égʰos →Every word from Ancient Greek ἄχος →