Pull the wool over someone’s eyes

To trick or deceive someone, the first known citation is American from c.1839 but the origin is obscure. One theory is that it derives from the habit of wearing woollen wigs, which could slip over one’s eyes, but this is dubious because the wearing of wigs, particularly in America, had largely fallen away by 1839. Another explanation is that wool refers to woollen caps, which could be pulled down over the eyes. Caps, however, were made from all sorts of material beside wool, so why was the expression not ‘pull the cap over someone’s eyes’? A much more plausible explanation is simply the pulling down of a person’s hair over their eyes. This makes better sense especially as ‘wool’ is recorded as slang for hair in America at that time.