Ric Ocasek from the Cars was known to use a thesaurus from time to time while writing his lyrics and, I'm sure, we all know someone who's used a rhyming book for help!
Ok, it actually took a little bit of hacking (I used to be able to open the video in a new tab to see who this was supposed to be, but now the link only goes to YouTube's home page!)...
Is this the right video Paulo? (David Sylvian - Orpheus)
You know you're going to screw up your member name if you ask questions like that! ?
As for me, usually one of the two things was the inspiration, so that usually takes precedence. That said, it's always a back and forth process for me!