Early 17th century; earliest use found in Walter Raleigh (1554–1618), courtier, explorer, and author. Either from post-classical Latin imaginatorius imaginary (although this is apparently first attested later: 1658 or earlier), or independently from classical Latin imāgināt-, past participial stem of imāgināre imagine + -ōrius -ory. Compare Middle French ymaginatoire imaginary.