Green’s Dictionary of Slang

(Irish) a boy, a young man.

2015		L. McInerney Glorious Heresies 319: She said the feen was dead.
2019		A. Killilea Boyo-wulf at https://boyowulf.home.blog 31 Mar. 🌐 [N]ot nobody that knows, from the bais in the halls to the feens under the heavens.
2021		L. McInerney Rules of Revelation 21: [A] callow feen called Ryan Cusack, from whom she’d bought a fair amount of cocaine over the years.