late 14c., adewe, from Old French a Dieu, a Deu, shortened from phrases such as a dieu (vous) commant "I commend (you) to God," from a "to" (see ad-) + dieu "God," from Latin deum, accusative of deus "god" (from PIE *deiwos "god" (from root *dyeu- "to shine").
Originally it was said to the party left (farewell was to the party setting forth), but in English it came to be used as a general parting salutation. As a noun, "expression of kind wishes upon departure," late 14c. Compare the native parting salutation good-bye, a contraction of God be with ye.
updated on September 15, 2022
Dictionary entries near adieu