Where does “соло” come from?

соло (Russian) comes from Italian solo, from Latin sōlus, from Ancient Greek Σολοῦς.

Ancestry of “соло”, step by step

Step	Language	Word	Meaning
1	Italian	solo	alone, by oneself, unattended, unaccompanied,...
2	Latin	sōlus	—
3	Ancient Greek	Σολοῦς	—

соло — Etymology, Origin & Word History | Etymology Explorer