I'm not sure, do you think Billy Connolly requested a character name change then..? It does sound a rather comedic name for a murderer. I love Connoly as a comedian, and as an actor;(Mrs Brown),but felt he was mis-cast in this. The episode could have been so much better with a real sinister foil for Columbo.
Well funny you should bring this up. This is something me and my friend in work noticed years ago. My friend asked Billy himself about it (he holidays on the Scottish Island of Bute where we live and was staying at Mickey's local). Billy said he was asked what the name should be and he couldn't resist having a bit of a dig at the posh Scots who give their children surnames for first names (Finlay, Crawford). So from the horses mouth - yes he did make the name up.
In the original script, the character's name was Paradiso. I assume it was changed because Paradiso sounds too Italian for Billy Connolly to play, but why Findlay Crawford, or whose idea that was, I never knew. It sounds like you have solved that question!
Billy Connolly did a sketch where he mocked posh Scottish people with second names as first names "Crawford, have you seen Findlay?". When he was asked to suggest a name for his character he used those two names as the character was a posh Scot.