A priest talked to us about Matt.6:7, explaining that many of the pagan gods were known by many different names.
Apparently, they needed to guess correctly which name the ‘god’ chose to be addressed by that particular day if they wanted their prayers answered.
It was the habit of the pagans, when praying, to repeat prayers invoking the ‘god’ of their choice under various names.
Someone pointed out to me that when non-Catholic Christians get together and everyone says a prayer (eg before a meeting) they are very similar/repetitious in content. I have since experienced this for myself.
I am not saying these prayers are ‘vain repetition’, just that many of these same people believe that prayers like the Rosary fit that category, yet can’t see it in their own prayers.