It's the actor's job to make "fertile lies" clear - I've coached this song a number of times and it's not all that hard to do.
I don't see why Gabby wouldn't be smart enough to "throw the book" this way at her cheating husband - and I do think that's one of the points of the song - a sort of "ok, so you think you're such an expert writer - watch this, you schmuck." To me, the heightened theatricality of it is enough to justify the lyrics.
If we want to deep-think "lies/fertilize," I think we can interpret the latter word as "taking hold" - fertilization being the first step in the growth of a new being. So, "your lies don't take hold" or "your lies aren't cutting it" etc. I think it's clear enough, and it's a great way to button that chain of wordplay. |
