This paper focuses on the Backbone Thesaurus (BBT for short), a coherent overarching meta-thesaurus for the Humanities, under which specialist thesauri and structured vocabularies used across scholarly communities can be integrated and form a thesaurus federation. Its core feature is that it promotes alignment of cutting-edge terminology to the well-formed terms of the meta-thesaurus capturing general meanings. The BBT favours a loose integration of multiple thesauri, by offering a small set of top-level concepts (facets and hierarchies) for specialist thesauri terms to map to. This way, it enables cross-disciplinary resource discovery, while ensuring compatibility with thesauri that cover highly specific scientific domains and areas of knowledge in development.