> From a noted local Scottish fiddler: She was singing in front of hundreds,
> on tour in her youth and got to part of a song about a lass disgusted with the
> men. Instead of singing," Before I'd have a man, I'd rather take a parrot",
> she sang,"Before I'd take a man, I'd rather take a carrot". it took a beat for
> all, including her to realize the implication.

You're thinking of "The Old Maid in the Garret". Both endings are traditional, but you more often hear "carrot" these days. If there was a mistake, it was just doing the wrong version for the occasion.

[The Parting Glass]
: I've got a theory that it's a pre-hanging song anyway, by someone who is going
: to be strung up in the morning

Sir Walter Scott thought it was exactly such a monologue, for the Border reiver Thomas Armstrong, hanged in Edinburgh in 1601. He didn't have any evidence for this that we know about.