Etymology of laugardagr:

Compound of laug (“bath”) +‎ dagr (“day”), literally “bath day”. The former element is cognate with English lye

This article says it was for raw vegetables:

For our ancestors, the appendix most likely evolved to help them digest a diet rich in raw vegetables and cellulose, as it still does in many herbivorous mammals. Thousands of years ago it would have functioned as an extension of the cecum, involved in the bacterial digestion of fibrous plant materials.

Here is a longer version of this:

“And people did this, just like you, you and me. These people did not come from another planet. […] They were human beings, just like us. And it was not Hitler who arrested me, not Goering, not Goebbels. The grocer, the janitor, the tailor, the shoemaker, the baker, they suddenly got a uniform, a swastika armband, and there they were, the master race…”

From this site: nationalfonds.org/…/recollections-of-auschwitz-at…

Here is how they actually look: