This paper is concerned with the phonological origins of the linguistic variety known today as Scots. We begin with a review of traditional and more recent scholarship on this topic before describing the particular research project from which this paper arises. In Section 2 we examine the circumstances in which the nascent Scots language emerged, noting in particular how contact between multiple Germanic (Gmc) varieties complicates the identification of its most likely progenitor(s). Such complications lead us to consider the problem of origin from the perspective of one particular segment, that of Gmc *a. In Section 3 we, first, introduce this particular case study, then trace the development of the vowel in each relevant daughter variety. On the basis of our findings, we reconstruct the most likely developments of Gmc *a in Scots. An evaluation of the candidate scenarios follows in Section 4, where we conclude that the particular development of Gmc *a in Scots sits at the crossroads of contact-induced and internally-motivated change.