(SM) As far as I know it is. Are you from the America's or possibly The Antipode's? It arose because greengrocers often advertise their wares with the extraneous apostrophe, thus: Tomato's, potato's, cabbage's etc etc. Simple as that.
Continuing my tour of traditional British establishments this evening, some colleagues and I ventured out to play Bingo at a big Bingo Hall in Slough (not far from Slough Bus Station which features in the opening credits of 'The Office'). We got hostile stares from the regulars... we played two games (£5 very quickly spent, in my opinion, but we could have picked up £15,000 on one national game) and left to go mand find something to eat. But I have to say, the staff who explained how to play before we went in were great, and gracefully accepted our apologies for calling out two false alarms when we thought we'd won, as we made out early exit. It's a bloody complicated game, Bingo. Next office outing is either horse racing, or to the dogs in Walthamstow ;o)