To welch basically means to trick or deceive someone by not making a payment on a bet. For example, 'we had a bet of five pounds that I would be able to lift the heavy table all by myself, I did, but that crook welched me". It refers to the dishonouring of a bet by not paying the rightful owner the predetermined amount which he deserves for winning the bet. It is a petty offence, though not regarded as a criminal one, as it is simply bound by an informal oral agreement. Hence, the person who has been cheated cannot do much but deal with it in a manner that he deems correct in a personal way. Anyway, such bets do not concern of large amounts of money.
