The name 'Lythrum' is from the Greek 'luthron' meaning blood and may refer to either the color of the plant's flowers or its medicinal use as an astringent to stop the flow of blood.
'Salicaria' means 'willow', and the shape of purple loosestrife leaves is similar to that of willows.
The common name for purple loosestrife in French is 'salicaire', which likely gave rise to such common English names as blooming sally, red sally, and flowering sally.
Purple loosestrife has been used in treating many ailments including diarrhea, dysentery, fevers, constipation, and cholera.
Japanese beetles are fond of purple loosestrife, which may appear to attract these insect pests in a similar manner as many roses.