Surprise at length of Tocharian nouns

The Tocharian languages exhibit many examples of the lengthened grade in roots of nominal stems. We find forms that, on the one hand, descend from PIE paradigms in which lengthened grades are expected given our current understanding of ablaut patterns, e. g. TA sanwem 'jaws', which descends either from an acrostatic u-stem or from a PIE denominative o-stem that denoted appurtenance and was formed by vrddhisation. On the other hand, there are lengthened grades in Tocharian nouns that do come as a surprise as is the case with TB nem/TA nom 'name', if this goes back to a protoform PIE (star)h(1)neh(3)-mn. These unexpected lengthened-grade forms will be discussed especially in the context of the so-called Narten system.