Messerschmied (=Messerschmidt) is the german expresson for knifesmith. Knifesmiths were in former times present in every little town, in bigger towns there were more. Therefore it is unrealistic to hope, all families called "Messerschmidt" have there origin in one family. But if you find "Messerschmidts" in one region around a town, they could be relatives, but only "could be".