That pronunciation almost sounds as though it has a ‘r’ sound in it — second syllable.
French pronunciation is hard to write for English speakers. The “Dieu” part is one syllable, but, to me it sounds like 1.5 syllables. It’s as if you are starting to say a word that begins with a “d” and then switch to one that starts with a “j”. Does that make sense.
And, no, I did not know the word, although, I have seen them, of course in churches. There was a spectacular prie-dieu in the church of my childhood. I thought it was one of the most beautiful things I had ever beheld. It was in front of a statue of the Infant of Prague, whose lovely garments also appealed to me. I suppose some woman in the parish made them.