how do you get the short end of a stick if a stick only has one lenght

figure that one out, nerds

It's the end with the shorter width
pretty simples really

If we're sharing a stick but you only get the last 30% of it, that's how.

Before the invention of the bidet, people would often clean the shit out of their butthole with a rag on a stick. Obviously one would not randomly choose which end of the stick to hold while doing this, preferring, instead, to always hold the same end. The other end being covered in shit would be known as the shit end of the stick. The word short is merely a euphemism for the word shit in this case.

The phrase itself is very ancient. In the middle ages people would talk of getting the shit end of the staff, originally in reference to being raped but over time to refer to any deal where a person gets the worst of it, the proverbial shit end of the staff.

As often as thei see theim selfes to haue the shite ende of the staffe in their cause.

Nicolas Udall, c1542