IIRC fro ancient times there was circumcision in Europe and the mid east but not widespread. Definitely not just a Jewish practice though.

Eunuchs seem to be found in eastern court settings in ancient literature, eg Herodotus. They also appear in Byzantium but succesfull casration requires a certain level of medical ability or the death rate is too high, so i can't imagine they were terribkly common.

If you're castrating officials to make them trustworthy (ie no kids = no nepotism) then you need a fairly sophisticated wealthy society (eg Imperial China or the Persian Empire).

The Arabian Nights seems to suggest the Eunuch was a more common figutre in Islamic society from the sophisticated court setting to less wealthy or civilised areas.

If you're just hacking off balls so your womenfolk's slaves don't get her up the duff then the subject is more expendable so more folks from more backgrounds will do it.