Wot's the mater, Vav?

Mater is mother - the one who teaches us to read. I was surprised to see in Psalm 89 that there was a uniqueness in the phrase from generation to generation, for of course, generation is a common word - לְדֹר וָדוֹר (LDR VDVR). So I checked my algorithm to hope there was no bug - and it seems there was not. This is the only place of the 18 occurrences of וָדוֹר including one other in Psalm 89 where the mater is also in the word. Curious - don't you think?