a) On the Fiddle
here are a couple of proposed derivations of the 'cheating' meaning of the phrase 'on the fiddle', each of them having supporters who are firm in their belief. Let's take the oldest first. The expression is said by some to derive from the Emperor Nero, who famously 'fiddled while Rome burned' and was a byword for corruption and dishonesty. The second suggestion is that the 'fiddle' was the name of the raised edge of the square wooden plates used by sailors. If a sailor took a normal amount of food he was said to have a 'square meal' and if his plate was overflowing he was said to be 'on the fiddle'.