Monique might explain this better, being a native French speaker, but I was also taught it as Tradsinger has explained.
Normally a word like DIVIN would be pronounced (nearest English equivalent) DEEVUN - not reaaly enunciating the N but VUN being a nasal sound.
But, because the next word, Enfant, starts with an E, it becomes DEEVEEN.
Happens particularly in songs. Any clearer than boue now?