1historical A children's game in which a small object is passed between the hands by one of the players, and, the hands being suddenly closed, the other player is required to guess in which hand the object remains, sometimes with the reward for a correct guess of keeping it.
2Figurative and in figurative contexts. "to play (at) handy-dandy": to act secretively or frivolously.
3Exchange of one position or thing for another, especially in a rapid or continuous manner.
With (rapid) alternation of place, position, status, etc.; alternately, in turn.
Used in offering a choice, usually implying that the options are easy to confuse, or so similar that it makes no difference which is chosen.
Late Middle English (in an earlier sense). Reduplication (with variation of the initial consonant and suffixation) of hand.
Used for emphasis: especially handy or useful; wonderfully convenient.
Early 20th century; earliest use found in The Galveston Daily News. Either reduplication (with variation of initial consonant) of handy, perhaps influenced by dandy, or from handy + dandy, to form a rhyming compound.