'milfoil' originates from Middle English, specifically the word 'milfoille,' from Old French 'millefeuille,' where 'mille' meant 'thousand' and 'feuille' meant 'leaf.'

'millefeuille' transformed into the Middle English word 'milfoille,' and eventually became the modern English word 'milfoil.'

Initially, it meant 'thousand leaves,' referring to the plant's finely divided leaves, and this meaning has largely remained the same in modern usage.