Etymology

Late Latin primogenitura, from Latin primus + genitura birth, from genitus, past participle of gignere

Noun

1. The state of being the firstborn of the children of the same parents.
2. An exclusive right of inheritance belonging to the eldest son.

Quotations

Anglo-Saxon kings did not succeed on the basis of primogeniture. All the kings offspring were known as aethelings -- throneworthy -- and from this gene pool the royal family would select the aetheling who seemed best qualified for the job.
-- Danny Danziger, The Year 1000