I have seen these words in the song "Dragonborn" (or "Sovngarde", which personally is my favorite version), and found it strange that they'd come up with two words to mean the exact same thing ("when"), and use both in the same lovaas. So I looked at both words and how they are used in the song -- lingrah morah -- and I had an idea. Here are all the occurances of the word fod that I know of:

1. "...ahrk fin norok paal graan fod nust hon zindro zaan..."
2. "...tol fod zeymah win kein meyz fundein!"
3. "Nuz aan sul fent alok fod fin vul dovah nok..."

And here is the singular use of the word rul:

1. "...rul lot Taazokaan motaad voth kein!"

It appears, from the way we see each word used, that fod is used when referring to common nouns and rul is used when referring to proper nouns. Here, I'll bold the nouns modifying each "when":

"...ahrk fin norok paal graan fod nust hon zindro zaan..."
"...tol fod zeymah win kein meyz fundein!"
"Nuz aan sul fent alok fod fin vul dovah nok..."

"...rul lot Taazokaan motaad voth kein!"

Since I haven't read every single line of dovah dialogue or read every work of kruziik bron literature, I don't know if these two words are used anywhere else. I have looked through the Word Walls, nuz ni siivaan naan that would help or hinder my claim. Even if my theory is nonsense and the writers of the language never meant for the two words to be different in any way, it could make life a little less confusing for us next time we're trying to choose which "when".

Thoughts?

According to Prima Games's online list, rul is a "special case, used only when the word is the first in the sentence." Maybe it can be used at the beginning of verses in poetry, too, as seen in the song.

Really? Ruth, I thought I was onto something. Well, at least I know now! Thank you.