From Proto-Indo-European *h₂enǵʰ- (“narrow, tight”) via a neuter s-stem noun *h₂enǵʰ-os (“narrowness”)^[1][2] combined with the adjective-forming suffix *-tós (equivalent to -tus). Comparative data does not establish when the adjective was derived, but its form would hypothetically correspond to *h₂enǵʰostos in Proto-Indo-European and to *angostos in Proto-Italic or Pre-Latin: this became angustus by the Latin sound change of vowel reduction, which replaced *o with /u/ in non-initial closed syllables. The neuter s-stem noun (Proto-Indo-European *h₂enǵʰ-os, Proto-Italic *angos) would have evolved regularly in Classical Latin to *angus, *angeris if it had survived. Another word potentially derived from this noun is the name of the goddess Angerōna.^[3]

The root is also found in Latin angō and angor, and in German eng, Sanskrit अंहु (áṃhu), Old Church Slavonic ѫзъкъ (ǫzŭkŭ).

For the ending, compare onustus, venustus.

• (Classical Latin) IPA^(key): [aŋˈɡʊs.tʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [aŋˈɡus.t̪us]

angustus (feminine angusta, neuter angustum, comparative angustior, superlative angustissimus); first/second-declension adjective

1. narrow, strait (especially of local relations)
2. close, contracted, constricted, small, not spacious
3. (figuratively) short, brief
   • 8 CE – 12 CE, Ovid, Sorrows 5:

     Efficit angustos nec mihi bruma dies.

     Winter does not make the days short (for me).

First/second-declension adjective.

• artus, brevis, contractus

• lātus

• angiportus
• angor

• “angustus”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• “angustus”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• angustus in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
• Carl Meißner, Henry William Auden (1894) Latin Phrase-Book‎^[1], London: Macmillan and Co.
  • (ambiguous) credit is low throughout Italy: fides tota Italia est angusta
    
• Walther von Wartburg (1928–2002) “angustus”, in Französisches Etymologisches Wörterbuch, volumes 24: Refonte A–Aorte, page 575