The practice grew out of British common law. Before the
Norman invasion, thirteen or fourteen was considered the age of adulthood, at
least among the nobility. But during battles, it was observed that thirteen –
and fourteen-year-old nobles were not large or strong enough to carry the heavy
armor and lance used in fighting. The age was changed to nineteen and then raised
to twenty-one, because nineteen-year-olds who inherited estates did not gain
their property until two years later, owing to the lengthy legal processes
involved. (The Book of Answers, by Barbara Berliner)
