|Bampton Fair 2005, where some horses are still sold - By Martin Bodman [CC-BY-SA-2.0 (www.creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons|
"IN old fashioned markets it is customary to give luck money on an animal being sold by the farmer himself.
The practice is gradually dying out, as auctions are taking the place of private contracts. In some places a penny merely passes from the seller to the buyer, a practice arising, probably, from some superstitious belief. In some districts a shilling or half-a-crown is given as luck-money. In others again, a man will deal and give a certain sum for a cow or a horse with the proviso that five or ten shillings shall be returned for luck or chap money. The origin of this custom is unknown. Sometimes, when engaging a servant, a shilling is given to clench the bargain. This is called earnest money."