The name should begin with an 'S' and be an animal. That was the rule in the thirties - I believe the 'S' was allocated to Vickers, who had taken over Supermarine, and the animal was allocated to fighter types - I may be wrong on this, somebody correct me, please.
The Shrew was mooted, but it was changed to SPitfire soon after.
Would it have mattered - probably not. What's in a name anyway - a rose by any other name would be as sweet!
A