This article contributes to an ‘historical turn’ in security scholarship. It addresses imbalance in security studies’ attention to historical empirics, and argues against notions of temporal disjunct prevalent within the discipline. I employ a genealogical framework to clarify the interpellation of past and present; and I introduce the ‘conceptual archive’ as a lens for pursuing that interpellation in research. My thesis on the ‘conceptual archive’ represents a twofold contribution. Firstly, a conceptual contribution: I advance the ‘conceptual archive’ as a way of thinking about past-present interpellation (specifically, existing conceptual logics’ remodelling in arguments justifying new practice). Secondly, an analytical contribution: I propose the ‘conceptual archive’ as a tool for doing genealogy (a research programme with historicising promise, but one suffering nebulous operationalisation at present). I use the field of terrorism studies as an entry-point to these contributions: adopting a mixed-methods research design to trace British counterterrorism practices’ roots within an ‘archive’ of logics on Northern Ireland. I find 1970s British governments remodelled long-standing ‘archival’ vocabularies in their arguments for new security provisions: framing exceptional practices according to an accepted fabric of concepts.