'Cuckold'

Actually, it is an insult. Maybe today it's not an insult because the western world is a lot more liberal now, but in the time and place of the movie, it was something to be ashamed of. That's why all the people in the town shun him and look down on him, and it's always mentioned how's been "dishonored".

In southern-Italian/Mediterranean culture, cornuto (cuckold) was THE biggest insult you can throw at someone either verbally, by act or by gesture (the index and pinky finger raised from a closed fist representing a bull's head. Cornuto="he who's got horns on his head"), it's a sacrilege of the sanctity of the family and was the number 1 cause for 'honour killings' for centuries (although the practice is pretty much faded now).

If you want some more background on this just go see the classic opera "Cavalleria Rusticana".