Through the use of an innovative methodological framework combining typology, comparative linguistics, historical morphology, and quantitative etymology, this book presents a diachronic analysis of the morphology of the Germanic strong verbs as well as a quantitative and up-to-date picture of the etymological connections between the strong verbs and the Indo-European parent language. It brings out the drastic transformations of the inherited verb system and shows that there are considerably more non-etymologized Germanic strong verbs than hitherto assumed, with telling implications for the genesis of the Proto-Germanic language.