English 'goodbye' is a contracted and reanalysed form of 'God be with ye,' a 16th-century farewell blessing whose divine invocation was gradually worn away by phonological reduction and then replaced by 'good' through analogy with other time-of-day greetings.
A farewell expression used when parting from someone.
A contraction of 'God be with ye' (or 'you'), first attested in the 1570s. The phrase was shortened progressively through 'God b'w'y,' 'godbwye,' and 'goodbye,' with the first element eventually reinterpreted as 'good' by analogy with 'good day,' 'good morning,' and 'good night.' The parallel with French 'adieu' (to God), Spanish 'adiós' (to God), and Italian 'addio' (to God) is structural but not etymological — all independently developed religious farewell formulas that placed the parting