This paper provides an overview of different approaches to the linguistic problem that the origins of PIE root extension present. Accepted definitions of root extension, like the one given by B. W. Fortson IV, “extra phonetic material (one or two sounds) added on to [roots], generally without any discernable change to the meaning of the root”1, shirk the question of why the simple root gets extended, and whether this process is governed by any definable principles.