I was wondering the same thing; I checked the French dictionary on my desk and "crépir" (which would be the expected derivative of "crespire") means "roughcast"

I was wondering the same thing; I checked the French dictionary on my desk and "crépir" (which would be the expected derivative of "crespire") means "roughcast", or plastering/cementing without smoothing the surface. I also found a Portuguese word "crespo" meaning something like "ragged". So I can sort of make sense of the phrase "quis crespit crespulum" in context as "those in a rough spot leave rough edges". But I'm not at all confident of that analysis.