The defender joined from League of Ireland Premier Division side Shelbourne FC on a three-year deal for an undisclosed fee in the summer of 2024.
The Dubliner made close to 70 appearances for Shelbourne.
A highly regarded player, Gavin picked up a Young Player of the Year award in 2023, while also being nominated for the award the season before and has become a highly consistent performer and respected player in the Irish League.
He made his competitive debut for Aberdeen in a 3-0 Premier Sports victory over Queen of the South in July 2023.