early 12c., "a fortunate day," also, generally, "good fortune;" from good, adj. + day, n.. As a salutation in parting, haue godne day "have good day" is recorded from c.1200; as a greeting from late 14c. Good morning is from late 14c. as a salutation, gode morwene. Good night, also goodnight as a salutation is from c.1200; as an exclamation of surprise from 1893.