Plasma cell disorders are important in the differential diagnosis of acute kidney injury and of renal impairment with proteinuria. One or more of several mechanisms can be involved, such as cast nephropathy, deposition of monoclonal immunoglobulins, formation of amyloid fibrils, hypercalcaemia, hyperuricaemia and a variety of tubular syndromes. Various tests, such as serum electrophoresis and immunofixation, assays for serum immunoglobulins and free light chains and tests for urinary paraproteins, also known as ‘Bence Jones protein’, are routinely employed in clinical practice. Scribbling these two words on a laboratory form (or ticking a box on a computer screen) raises questions: what is being tested and who is ‘Bence Jones’. Does this eponym honour one physician or two, or perhaps a patient? Here, we provide some insights into the history of this commonly used eponym and aim to put it into context.