The noun eavesdrop for the ground receiving drip from eaves is Old English, and medieval legal records penalize eavesdroppers, people who stand within the drip area to overhear. Henry Blackstone-era legal tradition kept the term for the nuisance. The verb in its modern listening sense is attested from the seventeenth century.
The colorful version says medieval law set fines for eavesdropping because walls were thin and honor was touchy, which is broadly true in spirit. The specific statutes quoted online are often garbled; the real record is local nuisance law, not a national anti-listening act.
The observation writes itself in the surveillance age: the drip zone is now digital, and everyone with a phone stands permanently under the eaves. The old law assumed you had to choose to stand there.
Privacy law, architecture, and weather all hid inside one word. What is the modern drip zone, and who is standing in it?