Are yams and sweet potatoes the same?
1520s, from Medieval Latin dictionarium "collection of words and phrases," from Latin dictionarius "of words," from dictio "word" (see diction). Probably first English use in title of a book was in Sir Thomas Elyot's "Latin Dictionary" (1538) though Latin Dictionarius was so used from early 13c. Grose's 1788 "Dictionary of the Vulgar Tongue" has "RICHARD SNARY. A dictionary."