Etymograph

English

certainly

Certainly comes from Middle English certeynly, equivalent to certain + -ly.

  1. Middle Englishc. 1150–1500certeynly‘without doubt’
  2. Englishearliest quotation 1908certainly

attested reconstructed ? uncertain or disputed

Lineage

  1. Middle Englishc. 1150–1500certeynly‘without doubt’
  2. Englishearliest quotation 1908certainly

Earliest quotation: 1908, William Blair Morton Ferguson, New York: “So this was my future home, I thought! Certainly…”

Formed from certain + -ly

Proto-Indo-European *krey- ‘to sift, separate’

…

Latin certus ‘fixed, resolved, certain’

Vulgar Latin *certānus

Old French certain ‘certain’

Middle English certeyn ‘specified, fixed’

English certain

Linked words

through Proto-Indo-European *krey- ‘to sift, separate, divide’

secret, crime, crisis, criminal, discrimination, critic, discretion, critique, discrete, riddle, discreet, hypocrite, discriminate, criterion, endocrine, discern, excrement, excretion, rime, incriminate, excrete, incrimination, recrimination, ridder, criterium, 47 more

through Latin certus ‘certain’

ascertain, certitude, 6 more

Today it means

adv In a way which is certain; with certainty.

Language periods are conventional ranges, not dates for this word.

Etymograph / Middle English certeynly / certainly