A previous discussion centred on the "Age of Consent". Another term that occurs in documents, especially Wills, is "Lawfull Years", i.e. the age of majority.

As a child I understood it to be 21 years, though today in most places and for most purposes it is more likely to be 18 years.

But what was it in say the 17th and 18th centuries.
I recently came across the Will of Dolin Dorghertie, Jurby, 1635, in which his under age son Thomas was named executor. Attached to the Will is a receipt dated 4 November 1646 when Thomas received his inheritance. Also attached is what is almost a baptismal certificate certifying that Thomas was baptized on 27 March 1630, i.e. he was 16 when he was considered of "Lawfull Age".