Etymograph

English

flat

Flat comes from Old Norse flatr ‘flat, level’, from Proto-Germanic *flataz ‘flat’, probably from Proto-Indo-European *pleth₂- ‘to spread’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*pleth₂-1‘to spread; flat’uncertain
  2. Proto-Germanicc. 500 BCE–200 CE*flataz1‘flat’reconstructed
  3. Old Norsec. 800–1350flatr1‘flat, level’
  4. Middle Englishc. 1150–1500flat1‘level’
  5. Englishearliest quotation 1589–1592flat1

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, English flat
  2. Earliest quotation in Wiktionary’s entry: 1589–1592, Christopher Marlowe, The Tragicall History of D. Faustus. […]: “Wag[ner]. Vilaine, call me Maiſter Wagner, and let thy…”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*pleth₂-Wiktionary, English flat‘to spread; flat’uncertain
  2. Proto-Germanicc. 500 BCE–200 CE*flatazWiktionary, English flat‘flat’reconstructed
  3. Old Norsec. 800–1350flatrWiktionary, English flat‘flat, level’
  4. Middle Englishc. 1150–1500flatWiktionary, English flat‘level’
  5. Englishearliest quotation 1589–1592flatWiktionary, English flat. Earliest quotation in Wiktionary’s entry: 1589–1592, Christopher Marlowe, The Tragicall History of D. Faustus. […]: “Wag[ner]. Vilaine, call me Maiſter Wagner, and let thy…”

The story

The algebraic sense was coined by Serre in a 1956 paper, originally as French plat.

Full etymology on Wiktionary

Linked words

through Proto-Indo-European *pleth₂-

plane, plate, plaza, platinum, collateral, lateral, piazza, plantain, plat, plaice, flan, 14 more

Another origin of flat

  1. Proto-Indo-Europeanc. 4500–2500 BCE*pleth₂-reconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*flatazreconstructed
  3. Proto-Germanicc. 500 BCE–200 CE*flatją‘floor’reconstructed
  4. Proto-West Germanicc. 200–500 CE*flati‘a flat surface’reconstructed
  5. Old Englishc. 450–1150flet
  6. Middle Englishc. 1150–1500flet‘dwelling’
  7. Scotsc. 1450–presentflet
  8. Englishtodayflat

Another origin of flat

  1. Proto-Germanicc. 500 BCE–200 CE*flatazreconstructed
  2. Proto-Germanicc. 500 BCE–200 CE*flatjaną‘to make flat, flatten’reconstructed
  3. Frankishc. 250–700*flattjan‘to move the palm of the hand’reconstructed
  4. Old Frenchc. 842–1400flatir‘to knock or strike down, dash’
  5. Middle Englishc. 1150–1500flatten
  6. Englishtodayflat

Today it means

adj Having no variations in height.

Sources

Sources: Wiktionary, “flat”. 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 *pleth₂- / flat

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