Where does “プサイ” come from?

プサイ (Japanese) comes from English psi, from Latin psi, from Ancient Greek ψεῖ — psi, the name for the twenty-fourth letter Ψ, ψ...

Ancestry of “プサイ”, step by step

Step	Language	Word	Meaning
1	English	psi	The twenty-third letter of Classical and Modern...
2	Latin	psi	—
3	Ancient Greek	ψεῖ	psi, the name for the twenty-fourth letter Ψ, ψ...