Help with Hesychius

In Hesychii Alexandrini Lexicon [V Century AC], the following is to be
found:

"bannas, basilens para Italiotais. oi de megistos arhcon"
Translation:
bannas, basileus of/by Italiotais. oi and big/great, very great [as
maximus/latin] archon

I have problems understanding the meaning of “Italiotais” [is this Italians?
Did the Greeks referee to today Italy with this term?] and “OI”.

Thank You for your help.

S o r i n