Introducing our Special Issue on marginalisation, this paper considers some of the challenges that this topic poses for legal scholars. The paper identifies that these challenges arise principally from the ambivalence of ‘marginalisation’ itself: at once an idea so broad that it arguably underpins the bulk of legal research (and socio-legal research in particular), but at the same time an idea that in practice too often quickly gives way to various other neighbouring ones: disadvantage, discrimination, disempowerment, exclusion, inequality, silencing, stigmatisation, victimisation and so on. This paper considers this ambivalence and traces etymological roots (and routes) by which we understand the margin, the marginalised and marginalisation.