“Father” is the most starkly simple introduction of a prayer in the entire tradition of Israel. It may be a child’s word, Abba, Daddy. It is a word of family intimacy. All of this prayer is thoroughly Jewish. I recommend that you look up Joseph Fitzmyer’s commentary 900-901, where he collects a series of quotations from various Jewish prayers that have almost exactly the same content. The difference is that there are a lot more words. Jesus’ prayer is starkly simple; it’s also starkly brief and intimate. These are the things that you would say to your father.