'single-form' is a Modern English compound from 'single' + 'form'. 'single' ultimately derives from Latin 'singulus' (via Old French and Middle English), where 'singulus' meant 'one each' or 'single'; 'form' comes from Latin 'forma', meaning 'shape' or 'appearance'.

'single' developed from Latin 'singulus' → Old French (e.g. 'sengle'/'single') → Middle English 'singel'/'sengel' → modern English 'single'. 'form' developed from Latin 'forma' → Old French 'forme' → Middle English 'form' → modern English 'form'. The compound 'single-form' is a straightforward modern English formation combining the two words.

Initially the components meant 'one each' (singulus) and 'shape' (forma); over time the compound has been used to denote 'one shape/one template' or 'having a single form', a literal extension of the original senses.