Origin: before 900; (noun) Middle Englishevesdrope,evesdripe,Old Englishyfesdrype; as v., probably back formation from eavesdropper,late Middle Englishevisdroppyr, apparently literally, one who stands on the eavesdrop in order to listen to conversations inside the house; see eave, drop, drip
(intr) to listen secretly to the private conversation of others
[C17: back formation from earlier evesdropper, from Old English yfesdrype water dripping from the eaves; see eaves, drop; compare Old Norse upsardropi]