An archaeological site is a palimpsest in which the evidence of the depositional episodes is destroyed through the excavation processes; all that remains are the artefacts and their documentary evidence manifested in registers, datasets, dig diaries and reports. While the reports may represent the end product of a specific excavation, the archaeological record tells a story; it is interpretative and dynamic, with later excavations adding new knowledge and narratives. Museums preserve the artefacts but unless the documentary evidence is preserved in standard formats, it cannot be easily re-used by the archaeology community to create that knowledge; nor can museums provide the narratives for the general public whose cultural heritage it is. This article presents a case study from the Ness of Brodgar excavations that examines possibilities for reconciling one part of the data of an archaeological dig, the small finds register (SFR) and its sparse amount of descriptive metadata, with the potentiality of data re-use and with the requirements of a museum that may have custody of the artefacts. It maps and enriches messy domain-specific ontologies to standard archaeological and cultural heritage ontologies and taxonomies using simple natural language processing, linked open data and the museum CIDOC conceptual reference model (CRM). This research, in examining the application of ontology mapping tools, explores common practices and processes that are useful in any discipline within the cultural heritage domain.