Wool tam question

I was looking into buying a wool tam to wear when I don't want my hair all over the place. I know wool encourages knotting- but now that I've looked at tams, it turns out there are at least three kinds of wool! Does the type of wool matter? I purchased one labeled "sheep's wool" (doesn't nearly all wool come from sheep? Perhaps the seller is just dumb) and one labeled "merino wool" and I saw some that were another type, as well. Does it matter? The merino wool one is much more comfortable, but I fear that the softness of it means it's not helping as much as the rougher sheep's wool. Any info?

updated by @rosie-ford: 01/13/15 09:07:08PM

I was mistaken- though I did see both "sheep's wool" and "merino wool", evidently I purchased a tam in "pure wool" and "peruvian wool". My question still applies, of course.

The term wool is very misleading I ordered a tam that said wool tam but it was acrylic. I was told by some wool experts that the term wool used by most refers to texture. According to them the correct term that should be used not to mislead people is yarn or knitting yarn. For example Alpaca wool is actually hair not wool but it is labeled as wool the same goes with other kinds of wool (cashmere is goat hair). I was told if the type of wool felts naturally then it's good for knotting up hair. I have a soft sheep wool tam and it does the trick.