It doesn’t do to be too curious or inquisitive.
The projecting edges of the roof of a house are known as the ‘eaves’, and the space of ground on which rainwater falls from the eaves is the ‘eavesdrop’ – or so it used to be called in the olden days. From ‘eavesdrop’ derived ‘eavesdropper’, one who stood within the eavesdrop in order to hear what was being said inside the house. It now refers to those who secretly listen to other people’s conversations; and, as the proverb suggests, what they hear about themselves is usually uncomplimentary!