What does the cowboy slang by nine mean?

The phrase "by nine" is not common cowboy slang. It's possible you've misheard or misinterpreted a phrase.

Here are some possibilities:

* "By and by": This means "soon" or "eventually".

* "Nine-tenths": A cowboy might say "nine-tenths" to mean "almost completely" or "very nearly".

* "Nine-iron": This refers to a golf club, not a common term in cowboy culture.

To help me understand what you're looking for, please provide more context.

For example:

* What was the situation where you heard this phrase?

* Who said it?

* What were they talking about?

With more context, I can help you figure out what "by nine" might have meant in that specific instance.