Etymograph

English

thumb

Thumb comes from Proto-Indo-European *tūm- ‘to grow’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*tūm-1‘to grow’reconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*þūmô1reconstructed
  3. Proto-West Germanicc. 200–500 CE*þūmō1reconstructed
  4. Old Englishc. 450–1150þūma1
  5. Middle Englishc. 1150–1500thombe1
  6. Englishearliest quotation 1849–1861thumb1

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, English thumb
  2. Earliest quotation in Wiktionary’s entry: 1849–1861, Thomas Babington Macaulay, London: Longman: “He gravely informed the enemy that all his cards…”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*tūm-Wiktionary, English thumb‘to grow’reconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*þūmôWiktionary, English thumbreconstructed
  3. Proto-West Germanicc. 200–500 CE*þūmōWiktionary, English thumbreconstructed
  4. Old Englishc. 450–1150þūmaWiktionary, English thumb
  5. Middle Englishc. 1150–1500thombeWiktionary, English thumb
  6. Englishearliest quotation 1849–1861thumbWiktionary, English thumb. Earliest quotation in Wiktionary’s entry: 1849–1861, Thomas Babington Macaulay, London: Longman: “He gravely informed the enemy that all his cards…”

The story

Also compare Welsh tyfu (‘to grow’), Latin tumēre (‘to swell’), Lithuanian tumėti (‘to thicken, clot’), Avestan 𐬀𐬨𐬏𐬙 (amūt, “strong”), Sanskrit तुम्र (túmra, “strong, thick”). The parasitic ‐b has existed since the late 13th century.

Full etymology on Wiktionary

Linked words

through Old English þūma

thimble

Today it means

noun The shortest and thickest digit of the hand that for humans has the most mobility and can be made to oppose (moved to touch) all of the other fingers.

Sources

Sources: Wiktionary, “thumb”. 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 *tūm- / thumb

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