Webster's Revised Unabridged Dictionary · 1913

Adieu

Adieu ({not transcribed}) , interj. & adv.

[Old English also adew, adewe, adue, French {not transcribed} dieu, from Latin ad to + deus God.]

Good-by; farewell; an expression of kind wishes at parting.

Adieu ({not transcribed}) , noun

A farewell; commendation to the care of God at parting. — Shakespeare