Why is someone who overhears conversations an eavesdropper?
“Snoop” might be more like it. There are few things more obnoxious than a person who deliberately tries to overhear private conversations. Whatever names (or insults) these sneaks deserve, “eavesdropper” is an odd-sounding word to use. This phrase is at least several hundred years old and its source is architectural. It comes from the eaves, the edge of a roof. The eavesdrip, or drop, was the space next to the wall where rain running off the roof fell to the ground. A person could overhear conversations by standing near the wall of a house in the eavesdrop under an open window. Then, presumably, he or she could take what they heard and drip it all over town.