Etymograph

English

must

Must comes from Middle English moste, from Old English mōste ‘had to’, past of mōtan ‘to be allowed; must’, and ultimately from Proto-Indo-European *med- ‘to measure’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*med-1‘to measure’reconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*mōtaną1‘to be allowed, may’reconstructed
  3. Proto-West Germanicc. 200–500 CE*mōtan2reconstructed
  4. Old Englishc. 450–1150mōtan1‘to be allowed, may; must’
  5. Old Englishc. 450–1150mōste1‘had to’
  6. Middle Englishc. 1150–1500moste1‘must, had to’
  7. Englishearliest quotation 1611must1

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, English must
  2. 2 Wiktionary, Old English motan
  3. Earliest quotation in Wiktionary’s entry: 1611, The Holy Bible, London: […] Robert Barker: “Arise, and go into the city, and it shall…”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*med-Wiktionary, English must‘to measure’reconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*mōtanąWiktionary, English must‘to be allowed, may’reconstructed
  3. Proto-West Germanicc. 200–500 CE*mōtanWiktionary, Old English motanreconstructed
  4. Old Englishc. 450–1150mōtanWiktionary, English must‘to be allowed, may; must’
  5. Old Englishc. 450–1150mōsteWiktionary, English must‘had to’
  6. Middle Englishc. 1150–1500mosteWiktionary, English must‘must, had to’
  7. Englishearliest quotation 1611mustWiktionary, English must. Earliest quotation in Wiktionary’s entry: 1611, The Holy Bible, London: […] Robert Barker: “Arise, and go into the city, and it shall…”

The story

From Middle English moste ("must", literally, "had to", the past tense of Middle English moten (‘to have to’)), from Old English mōste (‘had to’), 1st & 3rd person singular past tense of mōtan (‘to be allowed, be able to, have the opportunity to, be compelled to, must, may’), from Proto-Germanic *mōtaną.

Full etymology on Wiktionary

Linked words

through Proto-Indo-European *med- ‘to measure’

medical, model, modern, medicine, mode, mood, medication, meditation, module, med, remedy, modification, mold, mud, medicinal, mould, blackmail, medic, modulation, meditate, modal, modulate, modicum, modus, modulus, mete, modulo, modifiable, 30 more

through Proto-Germanic *mōtaną ‘to be allowed, to be permitted to, may’

mail, 1 more

through Old English mōtan ‘to be allowed, be able to, have the…’

mote, 1 more

Another origin of must

  1. Proto-Indo-Europeanc. 4500–2500 BCE*mus-‘damp’uncertain
  2. Latinc. 75 BCE–200 CEmuscus‘moss’uncertain
  3. Latinc. 75 BCE–200 CEmustus‘newborn, new, fresh, perhaps lit. 'wet'’
  4. Latinc. 75 BCE–200 CEmustum
  5. Old Englishc. 450–1150must
  6. Middle Englishc. 1150–1500must
  7. Englishtodaymust

Today it means

verb To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a failure or negative consequence.

Sources

Sources: Wiktionary, “must”; the older steps come from the Wiktionary entry for Old English motan. By Wiktionary contributors, CC BY-SA 4.0, via kaikki.org (dump of Oct 3 2026); text adapted and restructured. Language periods are conventional ranges, not dates for this word. License.

Etymograph / Proto-Indo-European *med- / must

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