I'm trying to refine my understanding of ON by studying inflexions
with a more phonological approach than I did before. This lead me to
the following question (please excuse the amateur I am if it is stupid
!) :
I remarked that some nouns (eg. skjǫldr, ǫrn) are subject to
u-mutations in the singular nominative and accusative, much like in
the strong neuter plural, but it is not always the case (eg. staðr).
Can it be explained in more details ? Were these nouns feminines at an
earlier stage of the language ? Does this have anything to do with the
"epenthetic u" of modern icelandic ? (maðr vs. maður)