The link you posted doesn't support that etymology; there are some proposed etymologies here https://english.stackexchange.com/questions/145376/what-is-the-orig

The link you posted doesn't support that etymology; there are some proposed etymologies here https://english.stackexchange.com/questions/145376/what-is-the-origin-of-long-and-short-in-finance https://english.stackexchange.com/questions/145376/what-is-t...