@Pitiless_Bronze , I didn't mean to laugh, but what a way to drive a point home.
I guess it is the oils in meat from fats (or fish guts!!) that make those awful ingredients penetrate leather. I have gone as far as to wash out a sheath with bleach to get that smell out and it didn't work all that well, plus it was really hard on the sheath. The old Schrade "Golden Spike" was a pretty good (not great) tool for hunting and cleaning, but was a good camp knife as well. But the leather sheaths they put on them were spectacular, and it even held a small stone for touch up sharpening. A small piece of guts wound up inside that sheath, and although I had "wiped" the knife, there was still enough fatty stuff on the blade and no doubt an odd bit of animal on it that got pushed in the sheath. I forgot about it, and when I pulled it out to freshen up the edge in prep for the next trip about 6 weeks later it was really rank.
It was so bad it made the Delrin plastic handle stink, too! They were inexpensive, so I just bought another one. About ten years of sitting in the gun closet empty and untouched, the smell went away.
I should have know better. My grandfather was a dedicated sport fisherman that lived on the Texas gulf coast for the sole reason of being able to fish several times a week. I remember asking my Dad why Grandad didn't put his knives in the sheath, but let the knife and the nice leather sheath bounce around in the tackle box. Sure thought of him when I saw your pic!
Robert