frock: [14] Frock is a Germanic word, although English acquired it via Old French froc. It originally meant ‘long coat or tunic’ – a sense reflected in the related Old High German hroc ‘mantle, coat’, and preserved in English frock coat and unfrock ‘dismiss from the office of clergyman’ (frock once having denoted a ‘priest’s cassock’, and hence symbolized the priestly office). Its application to a ‘woman’s dress’ dates from the 16th century. [frock etymology, frock origin, 英语词源]