What is the (probably Indo-European) origin of the latin suffix -idus, as in "acidus"? Are there any known cognates?

  • Wiktinary gives reference to “-idus” on page 821 of the Oxford Latin Dictionary (1st ed., 1968–82) (en.wiktionary.org/wiki/-idus#Latin)
    – Eleshar
    Dec 3, 2020 at 17:11
  • 2
    Depends on whether you believe in laryngeal metathesis in Italic. I don’t think there’s any real, across-the-board consensus; personally I favour the explanation that it’s from *tó-participles to laryngeal-final stems (predominantly statives, hence its affinity with the second conjugation), with laryngeal metathesis. Dec 3, 2020 at 17:20
  • @JanusBahsJacquet So the idea is Ht > tH > tʰ > d? Are there other examples of laryngeal aspiration in Latin? And why doesn't it happen in e.g. nōtus, nātus?
    – TKR
    Dec 3, 2020 at 23:00
  • @TKR Those are both syllabic laryngeals, so you wouldn’t expect it in those cases. The parade example is of course *stéh2-tlo-m > stabulum, where the metathesis is seen both in the quality of the consonant (b < θ) and the length of the vowel; the same is true if it’s *-eh1-tó- > -*e-tʰo- > PIt. *-eθo- > Lat. *-idus (with regular raising of both *e and *o). It’s not quite so straightforward across the board, and there are counterexamples, but to me it solves a lot more problems than it creates. Dec 3, 2020 at 23:44
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    @JanusBahsJacquet For non-syllabic Ht without metathesis cf. vātis, Brūtus, tūtus (if from tuh₂- as per de Vaan), and the suffix -tāt-. Stabulum is I believe usually derived from *sth₂-dʰlo-m, which seems more straightforward.
    – TKR
    Dec 4, 2020 at 2:57

1 Answer 1


Latin opposes participles with -nt- (active) to -d- (passive-stative).
If you believe in Kortlandt's effect, that is to say the alternation between *H1 and *d in a number of words and roots, then -d- in timi-d-us and -eH1- in tim-e-o are basically the same morpheme *-d- with and without Kortlandt's effect.

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