I think the song you've heard is called "Sylvie." It's here in my "A Bonnie Buch of Roses" songs of England Ireland and Scotland--a songbook with 150 songs from the Britsh Isles by Dan Milner and Paul Kaplan. It Goes: Sylvie, Sylvie, when none could see, Dressed in mens's clothing and gear so free, With a sword and pistol all by her side, To meet here true love, to meet her true love Sylvie did ride...The melody is the same as The Wild and Wicked Youth. The band Solas does a version of the "Wild and Wicked Youth" they call "Newry Town."