English
certainly
Certainly comes from Middle English certeynly, equivalent to certain + -ly.
attested reconstructed ? uncertain or disputed deepest recorded ancestor
- 1 Wiktionary, English certainly
- Earliest quotation in Wiktionary’s entry: 1908, William Blair Morton Ferguson, New York: “So this was my future home, I thought! Certainly…”.
Lineage
- Middle Englishc. 1150–1500certeynlyWiktionary, English certainly‘without doubt’
- Englishearliest quotation 1908certainlyWiktionary, English certainly. Earliest quotation in Wiktionary’s entry: 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, 45 more
through Latin certus ‘certain’
Today it means
adv In a way which is certain; with certainty.
Sources
Sources: Wiktionary, “certainly”. 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 / Middle English certeynly / certainly