English and Welsh bastardy laws
In the law of England and Wales, a bastard is an illegitimate child, one whose parents were not married at the time of their birth. Until 1926, there was no possibility of post factum legitimisation of a bastard.
Etymology
The word bastard is from the Old French bastard, which in turn was from Medieval Latin bastardus. In the modern French bâtard, the circumflex merely represents the loss of the 's' over time. According to some sources, bastardus may have come from the word bastum, which means pack saddle, the connection possibly being the idea that a bastard might be the child of a passing traveller. In support of this is the Old French phrase fils de bast loosely meaning "child of the saddle", which had a similar meaning. A more defined possibility is that such a traveller was a member of the corps de bast, referring to the division of an army who arrived in town with their pack saddles the night before the troops, and left the day after, so that they may deal with all of the provisions of an army, and even do advanced scouting. This meant that for two days, they had unfettered access to all of the women in town, and were therefore the ones most likely to be the cause of the town's illegitimate offspring.Common law origin
Bastardy was not a status, like villeinage, but the fact of being a bastard had a number of legal effects on an individual.One exception to the general principle that a bastard could not inherit occurred when the eldest son was born a bastard but the second son was born after the parents were married.
The Provisions of Merton 1235, otherwise known as the Special Bastardy Act 1235, provided that except in the case of real actions the fact of bastardy could be proved by trial by jury, rather than necessitating a bishop's certificate.