bear means “the brown one”. The common explanation is that bears were either objects of cultic veneration or seen as kinda human or some combination thereof, so their true name was hidden — as a measure of respect or fear or honor. or some combination of the three.
Allusive and indirect names then got applied to “bear” too — a common scholarly opinion is that “Beowulf” is “Bee-hunter”, a bear. (Though opinions differ there).
Your link doesn't support this. Latin and Greek are supposed to have preserved the Indo-European word; e.g. Spanish oso today descends directly from the word you're referring to.
Of course we don't know the oldest word(s) for anything, because the information is lost over time. Proto-Indo-European is as far back as we can reconstruct, but it's not like the ancestors of the Indo-Europeans couldn't speak.
Swedish has cognate "ulv" which is synonymous to "varg". It's not used much anymore, but I think it fell into disuse fairly recently. Reading fairy tales from 1800's and early 1900's you are bound to encounter it.
And alternate spelling "Ulf" is a top 50 first name in Sweden.
In summary I don't think a taboo is an explanation in this case.
EDIT: Oh and the word for werewolf is varulv.