The phrase 'dinned in to' means to persistently repeat or emphasize something to someone. Some synonyms for this term might include words such as 'hammered in', 'reiterated', 'emphasized', 'insisted', 'underscored', 'impressed upon', 'drummed in', 'ingrained', or 'instilled'. Each of these terms conveys a sense of repetition or insistence in conveying a message or idea. Whether it's a teacher trying to drive home a point to their students or a parent trying to impress a value upon their child, using strong language and persistence can help to ensure the message is understood and ingrained in the recipient's mind.