'single-seeded' is a compound of 'single' + 'seeded'. 'Single' ultimately comes from Latin 'singulus' (via Old French 'sengle' and Middle English 'single'), where 'singulus' meant 'one each'. 'Seeded' is formed from Old English 'sǣd' (seed) with the past-participle/adjective-forming suffix '-ed'.

'single' developed from Latin 'singulus' → Old French 'sengle' → Middle English 'single'; 'seeded' developed from Old English 'sǣd' + the adjectival/past participle suffix '-ed', giving the modern compound 'single-seeded'.

Originally the components meant 'one' (from 'singulus') and 'seed' (from Old English 'sǣd'); combined, the compound has long meant 'having one seed' and this core meaning has remained stable.