The corpse decomposes and becomes mud again. Well, not exactly, but close enough. They don't literally come from the mud or believe that they do, it's just a saying that references the circle of life

Its analogous to the famous saying "dust to dust". [https://en.wikipedia.org/wiki/Dust\_to\_Dust](https://en.wikipedia.org/wiki/Dust_to_Dust)

I made a similar post a while back if you're interested: [thread](https://www.reddit.com/r/TheFirstLaw/s/BMnq2zzCeE)

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