Originally this word had nothing to do with snooping.
Eavesdrop started off literally: first it referred to the water that fell from the eaves of a house, then it came to mean the ground where that water fell.
Eventually, eavesdropper described someone who stood within the eavesdrop of a house to overhear a conversation inside.Over time, the word obtained its current meaning: "to listen secretly to what is said in private."
So, I guess if you "eavesdrop" you're a big drip!!