1580s, mad +"Ž cap (“head"), literally “crazy head". Original literal sense “lunatic, crazy person", now used figuratively.
"Well, do you recognize your little madcap playmate?" asked the countess.
In 1590 he married Anne of Denmark: in 1592 his character suffered through the murder, by Huntly, of " the bonny earl o' Murray," suspected of favouring the madcap Francis Stewart, earl of Bothwell (nephew of Queen Mary's Bothwell), a man who made it his business to kidnap the king, and who presently, by the help of Gowrie's widow, seized him in Holyrood.
madcap antics both on and off the stage.
madcap slapstick comedy looks pretty funny from the trailer.