To break the news to someone most probably is the image of the medieval messenger who bears his message as a role of parchment, roled together and sealed. When he comes to the king he breaks the seal and reads the message to the king. He breaks the news to him, actually he breaks the seal and reads the news to him. This two-part expression was shortened, with to break from the first part and news from the second part. Astonishing that etymonline does not mention to break the news to someone.

To break the news to someone most probably is the image of the medieval messenger who bears his message as a roll of parchment, rolled together and sealed. When he comes to the king he breaks the seal and reads the message to the king. He breaks the news to him, actually he breaks the seal and reads the news to him. This two-part expression was shortened, with to break from the first part and news from the second part. Astonishing that etymonline does not mention to break the news to someone.