A gentleman sees a pretty (shepherdess), and lies with her (without her leave). She becomes pregnant. Some weeks or months later, the gentleman returns and claims her for his own
Note that this melody is used for two pieces, both called "Broom o' the Cowdenknow(e)s," and both Scottish: The ballad listed here, and a more lyric piece about a man who must leave home because he fell in love with a girl above his station.
Although the texts of this piece are generally quite late, the tune appears much older. BBI ZN2610, "Through Lidderdale as lately I went," registered in 1632, claims a "pleasant Scotch tune, called, The broom of Cowdenknowes" as its melody.
It's ironic to add that the tune you've almost certainly heard for this song (Bronson's #1) is from Playford, without lyrics -- and neither the Playford tune nor any of its immediate relatives in Bronson has a text (Bronson's group Aa includes six tunes; #4 has a single stanza of lyrics, the rest none -- and that stanza in #4 is the lyric version of the song, not the ballad!). - RBW