OK, here we go. I found this in a meme and decided to dig out the research paper.

It does exist.

Somebody actually tried it.

https://www.researchgate.net/publication/336186563_Experimental_replication_shows_knives_manufactured_from_frozen_human_feces_do_not_work

An Exercise in Poo-Tility: Scientist Tries to Make a Knife Out of Poop