Old hat

Old fashioned, passé, outdated, dates from the early 20th century when hats were a strong statement of fashion. Therefore, an old hat was more than likely to be treated with disdain. Before this, however, from the mid-18th century, it had a vulgar meaning. George Grose in his Classical Dictionary of the Vulgar Tongue published in 1785 has old hat listed as “a woman’s privities; because frequently felt”. (Grose’s dictionary is so full of puns and plays on words that one never knows when he is being serious.)