Labbe is mentioned as the equivalent of Labbé, Labé etc. in a dictionary of surnames that occur in Flanders and in Northern France. There are examples of Labbes already in 1393. Abbé could mean abbot, priest etc. and the name was occasionally given to people looking or behaving like an "abbé". Cannot find an internet-source however.
For Labé see Louise Labé the French poetess.