Where does “Bretagna” come from?

Bretagna (Italian) comes from Latin Britannia, from Ancient Greek Βρεττανία, from Ancient Greek -ῐ́ᾱ, from Proto-Indo-European -íh₂, from Proto-Indo-European -h₂ — Creates collective nouns, which refer to groups...

Ancestry of “Bretagna”, step by step

Step	Language	Word	Meaning
1	Latin	Britannia	Britain
2	Ancient Greek	Βρεττανία	the British Isles
3	Ancient Greek	-ῐ́ᾱ	{{l\|en\|-ia}}; "suffix forming abstract feminine...
4	Proto-Indo-European	-íh₂	—
5	Proto-Indo-European	-h₂	Creates collective nouns, which refer to groups...

Every word from Proto-Indo-European -h₂ →Every word from Ancient Greek -ῐ́ᾱ →Every word from Ancient Greek Βρεττανία →