I always read OG as "old guard", a literal translation of the Portuguese term "velha guarda", which has a similar meaning (the oldest people at a Samba school,

I always read OG as "old guard", a literal translation of the Portuguese term "velha guarda", which has a similar meaning (the oldest people at a Samba school, something like "seniors"). Since I've grown with Samba, OG = old guard = velha guarda was an intuitive translation, I never though of looking for a different expansion.