late Middle English (formerly also as ingross): based on en-, in- ‘in’ + late Latin grossus ‘large’. Sense 1 is from Old French en gros, from medieval Latin in grosso ‘wholesale’; sense 2 comes from Anglo-Norman French engrosser, medieval Latin ingrossare, from Old French grosse, medieval Latin grossa ‘large writing’, with reference to clerks writing out documents in large, clear writing.