Farewell is a parting expression that may convey the wish “be strong,” “rejoice,” or simply “take leave.” It can occur at the close of a letter or when people separate from one another.
In letters it expresses a parting wish for strength or rejoicing. In narratives it describes bidding farewell or taking leave of people at home or elsewhere.
The English expression originally conveyed a wish for those faring forth or traveling. The underlying Greek expressions include be strong, rejoice, and separate oneself or take leave.