I can spot a joke, but that seemed plausible enough for me to look up. Sadly, that's not given on etymonline.com as the etymology, but as it lists the OED as be

I can spot a joke, but that seemed plausible enough for me to look up. Sadly, that's not given on etymonline.com as the etymology, but as it lists the OED as being uncertain about the commonly reported etymology, there may yet be hope.