The East Baltic languages are well known for their conservative phonology as compared to other Indo-European languages, which has led to a stereotype that the Balts developed in isolation without much contact with other speech communities. This book challenges that view, taking a deep dive into the East Baltic lexicon and peeling away the layers of prehistoric borrowings in the process. As well as significant contact events with known languages, the lexicon also reveals evidence of contact with unattested languages from which previous populations must have shifted.