'platelet' originates from English, specifically formed from the noun 'plate' (from Old French 'plate', ultimately from Latin/Greek roots 'platus'/'platys'), where 'plate' meant 'a flat piece', and the diminutive suffix '-let' (from Old French '-let'), where '-let' meant 'small'.

'platelet' changed from the compound formation of 'plate' + the Old French diminutive '-let' used in Middle English to indicate a small or diminutive object, and eventually became the modern English word 'platelet'.

Initially, it meant 'small plate' or 'small flat piece', but over time it evolved into the biological sense of 'a small blood cell fragment involved in clotting'.