Early 17th century; earliest use found in George Chapman (?1560–1634), poet and playwright. Origin uncertain; perhaps from classical Latin imāgin-, imāgō image + -ous, or perhaps from imagine + -ous. Compare classical Latin imāginōsus full of pictures or images (in an isolated example in Catullus (41. 8) where the reading is disputed), in post-classical Latin also contriving or scheming.