1Positive and negative statement (or command); affirmation and denial (or injunction and prohibition).
2historical A name given to King Richard I of England (1157–99). Chiefly in "Richard Yea-and-Nay".
The motivation for the name is unclear.
1Of indefinite or indeterminate character; changeable; ambiguous.
2rare Of a person: tending to affirm or deny indifferently or according to expediency; hesitating, vacillating, undecided.
Late Middle English; earliest use found in The Wycliffite Bible (early version). From yea + and + nay.