Grass widow

The word appears in the Germanic languages in different forms and senses, evidently being ancient, but the oldest (both 16th century) are English grasse wydowe and Middle Low German grasswēdewe, both meaning “girl who has lost her virginity, harlot”. Therefore “grass” in all likelihood refers to a bedding for premarital sex. Compare the expression green gown (“loss of virginity”). The girl became a “widow” in the sense that she was neither married nor a virgin. The sense then developed through “married woman who has relations in her husband’s absence” to the contemporary, softened meaning. Compare Dutch grasweduwe, Swedish gräsänka, German Strohwitwe. Etymonline cites the book Vocabulary of East Anglia (1830) by Rev. Robert Forby, which records the term in that region as essentially referring to a woman abandoned after an informal marriage.