vroom (nl)
Fragment of a discussion from User talk:Rua
{{bor|xx}} means that the term was borrowed into language xx. If the word was borrowed into Middle Dutch, then {{bor|dum}} would be ok. But of course it can only be borrowed once in a language's history, so any subsequent languages would use {{der}}.
Yes, there is a normalisation scheme for Middle Dutch, it's at WT:ADUM. In general, you can find a lot of information on practices and rules for individual languages on these "About..." pages.