‘Origins’, stated Donnchadh Ó Corráin of the genealogical tradition in medieval Ireland, ‘are not simply origins’. Once ignored or dismissed as antiquarian indulgences, this vast body of royal pedigrees, king-lists and poetic panygyric is now recognised as having served a very real service for its patrons as the proving documents of power. In a society where authority was largely based on dynastic credentials, ‘an origin is the demand the present makes upon the past, not knowledge for its own sake – a much more recent historical pretence’. This function of historical writing, as architect as well as record of the past, was also easily recognisable to the Anglo-Norman world which provided the incomers to Ireland after 1169, in which prestige and property descended in vertical lines, and for whom lignage was an equally pervasive preoccupation. National pseudohistories gave roots to the authority of post-Conquest kings of England by connecting them with a legendary British past. Genealogies of noble families, fusing romance with record, claimed dignity for their sponsors by emphasising contiguity with their progenitors.

If a burden could be placed on memory by the present, however, so too an origin could be a mandate of the past on the here and now. Individual agency in medieval Britain and Ireland was often shaped by a concern with living up to, or living down, one's ancestors. When inherent characteristics of nobility were believed to pass from generation to generation, consanguinity with an illustrious forebear was still the basic qualification of nobility, and ‘no ceremony could make up for the lack of exalted blood-lines’. The inheritance of moral as well as physical qualities was also accepted in Gaelic Ireland. In the first recension of the epic Táin bó Cúailnge (‘The cattle-raid of Cooley’), the antagonist Medb, queen of Connacht, lists Maine ‘Cotageib Uile’ (‘grasp them all’) among her seven sons: is éside tuc cruth a máthar & a athar & a n-ordan díb línaib (‘he it is who has inherited the appearance of his mother and father and the dignity of them both’).

Membership of a noble family was in this way double-edged. Deference or allegiance could be claimed simply by virtue of one's name, and even before his leading role in Anglo-Norman intervention in Ireland, Richard de Clare (Strongbow) was already ‘set apart by his ancestry, born of the noble stock of the Clare family’.