What fabric was favoured by polar explorers in the early 20th Century?

Even though gabardine was used in a few extreme cold situations during the 20th century, but ALL extended extreme cold outfits rely on layers for warmth. Wool was almost always used as the interior layer to trap heat... regardless of the various external wind breaking garments available at the time.

But gabardine is made with wool, so wouldn’t the answer wool also be correct?!

Wow!! Didn't know such fabric exists