True? NO! In the old days men would stand outside the courtrooms with straw in their shoes. That would indicate their willingness to be a false witness and lie in front of the judge. So a straw man became someone who lied deliberately?

Its nonsense.

Though repeated in websites and books - I saw it recently in a book about London in the early 1700s - not a single legitimate source attests to the concept.

And frankly you might wonder just how credible men standing around advertising they would give false witness might be? At best it's a joke; more likely just another urban myth.