Etymograph

English

bissextile

Bissextile comes from Latin bisextilis/bissextilis ‘bissextile year’, from bisextus ‘intercalary day’, and ultimately from Proto-Indo-European *dwóh₁ ‘two’.

  1. Proto-Indo-Europeanc. 4500–2500 BCE*dwóh₁1‘two’reconstructed
  2. Proto-Indo-Europeanc. 4500–2500 BCE*dwís1‘twice, doubly’reconstructed
  3. Proto-Italicc. 1500–700 BCE*dwis1‘twice’reconstructed
  4. Old Latinc. 700–75 BCEduis1
  5. Latinc. 75 BCE–200 CEbis1‘twice, two times, on two occasions, in two ways’
  6. Latinc. 75 BCE–200 CEsextus1‘sixth’
  7. Latinc. 75 BCE–200 CEbisextus2‘intercalary day’
  8. Latinc. 75 BCE–200 CEbisextilis/bissextilis2‘bissextile year’
  9. Englishearliest quotation 1878bissextile2

attested reconstructed ? uncertain or disputed deepest recorded ancestor

  1. 1 Wiktionary, Latin bisextus
  2. 2 Wiktionary, English bissextile
  3. Earliest quotation in Wiktionary’s entry: 1878, W.S.B. Woolhouse & al., Vol. IV: “The additional day which occurred every fourth year [after…”.

Lineage

  1. Proto-Indo-Europeanc. 4500–2500 BCE*dwóh₁Wiktionary, Latin bisextus‘two’reconstructed
  2. Proto-Indo-Europeanc. 4500–2500 BCE*dwísWiktionary, Latin bisextus‘twice, doubly’reconstructed
  3. Proto-Italicc. 1500–700 BCE*dwisWiktionary, Latin bisextus‘twice’reconstructed
  4. Old Latinc. 700–75 BCEduisWiktionary, Latin bisextus
  5. Latinc. 75 BCE–200 CEbisWiktionary, Latin bisextus‘twice, two times, on two occasions, in two ways’
  6. Latinc. 75 BCE–200 CEsextusWiktionary, Latin bisextus‘sixth’
  7. Latinc. 75 BCE–200 CEbisextusWiktionary, English bissextile‘intercalary day’
  8. Latinc. 75 BCE–200 CEbisextilis/bissextilisWiktionary, English bissextile‘bissextile year’
  9. Englishearliest quotation 1878bissextileWiktionary, English bissextile. Earliest quotation in Wiktionary’s entry: 1878, W.S.B. Woolhouse & al., Vol. IV: “The additional day which occurred every fourth year [after…”

Linked words

through Proto-Indo-European *dwóh₁ ‘two’

two, doubt, vice, twin, dual, duo, vicious, duet, twain, dubious, disparate, twig, deuce, bes, 20 more

through Proto-Indo-European *dwís ‘twice, doubly’

defeat, diplomacy, betwixt, 11 more

through Proto-Italic *dwis ‘twice’

binary, binocular, 4 more

through Latin bis ‘twice, two times, on two occasions, in two ways’

bis, biceps, 3 more

Today it means

adj Being or having an intercalary day, particularly the quadrennial leap day of the Julian and Gregorian calendars traditionally placed as a "second sixth" day before March 1st.

Sources

Sources: Wiktionary, “bissextile”; the older steps come from the Wiktionary entry for Latin bisextus. 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 *dwóh₁ / bissextile

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