My definition for OG actually reflected real usage in Ireland, but maybe only in Irish, or (likelier) not well enough documented in English to make it into a dictionary. That usage formed the basis of one of my mother's favourite stories, about her first day at a new school, where the class teacher was finding out the names of her new charges. One of them was Máire, from the west of Ireland, called Máire Óg to distinguish her from her mother, and probably also from her grandmother, who might well have been called Sean Mháire, though perhaps not to her face.
NUN. Well child, what is your name, dear?
MÁIRE ÓG. Me name is Óg, Mother.
NUN (mildly indignant). Óg? But that’s not a saint’s name!
MÁIRE ÓG (puzzled). But, sure I’m no saint, Mother.