-turio

• (possibly) -urriō

Uncertain. Latin vowel reduction probably caused any short vowel in a word-internal open syllable to evolve regularly to -e- before -r- (compare -fer from Proto-Italic *-foros, socerī from Proto-Italic *swekurī^[1]), which suggests that this suffix had a comparatively recent analogical origin. (An alternative opinion holds that -u- was regularly retained before -r-, but Parker 1986 argues that examples like augurium can be explained by analogy, e.g. to the nominative augur.)

• Possibly from Proto-Indo-European *-tew- (as in the supine) + *-rós.^[2] Possibly compare -tūrus and/or -tūra. According to De Melo 2007, Risch 1954 postulates the construction goes back to an unattested *saturiō (“to be full”) from satur, used as the basis for an analogical ēsuriō, originally with the sense "to be hungry" but then evolving to "to want to eat".^[3]
• Possibly from -tor- (the original oblique stem of the agent suffix -tor, from Proto-Italic *-tōr) +‎ -iō, from Proto-Indo-European *-yéti (denominative suffix).^[4]

• (Classical Latin) IPA^(key): [tʊ.ri.oː]
• (modern Italianate Ecclesiastical) IPA^(key): [tu.ri.o]

-turiō (present infinitive -turīre, perfect active -turīvī, supine -turītum); fourth conjugation

1. Forms desiderative verbs from other verbs.

   ‎pariō (“to bring forth”) + ‎-turio → ‎parturiō (“to be in labour”)

   ‎nubō (“to veil, marry”) + ‎-turio → ‎nupturiō (“to wish to wed”)

   Sulla → *sullō (“I do as Sulla did”) → sullaturiō (“pessimistically jocular: I wish to imitate Sulla”)

• Usually formed on the same stem as the supine/perfect participle; but adulēscenturiō is an exception.
• The -turio aspectual compounds are sometimes referred to as desiderative; the Late Latin era grammarians Priscianus and Diomedes use the phrase meditative, or verba meditativa, for this construction.