An archaic spelling of 'eavesdropper,' a person who secretly listens to other people's private conversations.
From Middle English combining 'eaves' (the overhanging part of a roof) with 'dropper' (one who drops or stands). Originally referred to someone literally standing under the eaves.
In medieval times, if you stood under someone's eaves where rainwater dripped, you could hear conversations through the windows — and you'd get soaking wet doing it, which is pretty dedicated spying.
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