In Etymonline, the etymology of primogenitor (and primogeniture) is very similar to progenitor. The word's meaning: Ancestor or forefather.

However, nowhere do I find the reason of the split from the word progenitor. Why does such word exist? When and where (near the 1650s) did it first appear? What is the correlation to the primogeniture succession law?

In a related manner, what is the difference to progenitor? When would one use one or the other?

Edit: Is the assertion that progenitor means the ancestor of a person, while primogenitor means the initial common ancestor of a people, correct?
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    I wouldn't recommend using it at all - it's a very obscure word! Jun 6 at 12:28
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    Exactly. And you never will find the link to any other word, because the information is buried in the past motions of millions of tongues now dead. Historical linguistics is like doing archaeology on ghosts instead of bones. Jun 6 at 12:32
  • So could I consider Primogenitor, basically an obsolete word? How pitiful.. Jun 6 at 12:34
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    Well, the Merriam-Webster dictionary does recognise 'primogenitor'; under its 'History and Etymology' it says 'borrowed from New Latin prīmogenitor (Medieval Latin, "eldest son"), from prīmo- (in Late Latin prīmogenitus "firstborn," prīmogenitūra "condition of being the firstborn") + Latin genitor "father, parent, originator" — more at PRIMOGENITURE, PROGENITOR'
    – HappyJoy
    Jun 6 at 22:37

1 Answer 1


Looking at the Cambridge English Dictionary online, it does not recognise the word primogenitor. There is a word Primogeniture. Primogeniture is the monarchical system of replacing one deceased monarch with their 'first born' child.

Merriam Webster does cite the word in the question, with a usage in 1643, celebrating the bicentenary of the founding fathers:

the family held a huge reunion to mark the 200th anniviersary of their primogenitors' arrival in America.

I am afraid that this usage looks like a malapropism or perhaps misspelling for the word progeniture. MW's definition confirms that diagnosis.


The word progenitor means precisely that. The definition of primogeniture in Cambridge is

the custom by which all of a family's property goes to the oldest son when the father dies.

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    Primogenitor is in the OED meaning "A person from whom another is originally descended; the earliest ancestor, esp. of a people; a forefather, a progenitor. Also in extended use." the etymology is from post classical Latin. Jun 8 at 12:15

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