Etymologically

Etymology and origin of the Latin word obsidium

Confidence
Established
Formation
Derivation
First attested
c. 250–184 BC, Plautus
Ultimate origin
Proto-Indo-European (*sed-)
Etymology tree
inherited borrowed derived
Latin obsideo
Latin obsessio
Latin obsidium

Forms

obsidium n (genitive obsidiī or obsidī); second declension[1] It is also spelled opsidium.[2]

Etymology

It is from Latin obsideō (“to besiege”) + -ium, formed like praesidium.[2][3] obsideō is a compound of sedeō (“to sit”), which de Vaan traces to Proto-Italic *sed-ē- (“to be seated”) and Proto-Indo-European *sed-eh₁- (“to be seated”), from the root Proto-Indo-European *sed-, comparing Ancient Greek ἕζομαι (hézomai, “to sit down”).[4] Varro explained it as a besieging that keeps the enemy from getting out, and Festus defended it as correctly formed like subsidium.[5][3]

Earliest recorded meaning

Plautus has it first, in the Bacchides: “the cause for which I now lay siege to Ilium”.[2][6]

Semantic evolution

It is a siege or blockade.[2][1] Lewis & Short note that it is mostly ante-classical and post-Augustan, and that Cicero and Caesar use obsidiō instead.[5] Columella extends it to a keeper's careful watch over bees and to the lying in wait of men who steal poultry.[2]

Timeline

  • c. 250–184 BC – Plautus of the siege of Troy.[2][6]
  • 116–27 BC – Varro explains the word.[5][6]
  • 1st century AD – Columella of watchfulness and of lying in wait.[2][6]

Meanings

Noun

  1. A siege, blockade, investment.[2][5][1]
  2. Careful guard, watchfulness.[2]
  3. Lying in wait, ambush.[2]

Word family

  • obsidiālis

Usage notes

A separate noun obsidium, “the condition of a hostage”, was formed from obses, “hostage”; it is found only in Tacitus, of Meherdates, who had been given to the Romans as a hostage.[2][5][6]

References

  1. ^ a b c Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k Glare, P. G. W., ed. (2012), Oxford Latin Dictionary, 2nd ed., Oxford: Oxford University Press
  3. ^ a b Thesaurus linguae Latinae (1900–), Leipzig: Teubner; Berlin: De Gruyter; open-access ed., Munich: Bayerische Akademie der Wissenschaften
  4. ^ de Vaan, Michiel (2008), Etymological Dictionary of Latin and the other Italic Languages, Leiden Indo-European Etymological Dictionary Series 7, Leiden; Boston: Brill
  5. ^ a b c d e Lewis, Charlton T.; Short, Charles (1879), A Latin Dictionary, Oxford: Clarendon Press
  6. ^ a b c d e Köbler, Gerhard (2010), Lateinisches Abkunfts- und Wirkungswörterbuch für Altertum und Mittelalter, online ed., koeblergerhard.de
Cite this entry

“Obsidium.” Etymologically, 19 Oct. 2026, etymologically.com/la/obsidium. Accessed 20 Oct. 2026.

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