In old westerns the slang word landagoshin is used what does it mean?

The word "landagoshin" is not a real word, and it is not used in old westerns. There is no evidence of it appearing in any Western films, novels, or historical documents.

Perhaps you are thinking of a different word that sounds similar, or you may have misheard something.

It's possible you're thinking of a made-up word used in a specific Western film or show that wasn't widely adopted. If you can remember any details about the context, like the film's title or the scene where it was used, it might help to identify the word you are thinking of.