What was written on sword blades?

In earlier medieval swords inscriptions are frequently very confusing or don't make sense. There are many words misspelled and strange (to us) abbreviations abound. This is particularly the case in times and places where most people were illiterate and in which the person inscribing the blade was probably just copying something someone else had written down without being able to read themselves. In those cases the writing was probably more akin to a magical device or symbol than something like a modern makers mark. In fact, prior to the Renaissance it was rather uncommon for craftspeople to sign objects that they made and if there was a name on the blade it was more likely to be the name of the person who bought the blade or of the person they served such as a king or lord.