Where does “suddenly” come from?

Suddenly comes from Middle English sodeinliche, formed with the Middle English adverbial suffix -ly from Middle English sodein, which derives from Latin subitaneus meaning "happening without warning," itself formed from Latin sub and Proto-Indo-European līg-.

suddenly (English): Happening quickly and with little or no warning;...

Definitions

  1. Happening quickly and with little or no warning;...

Ancestry of “suddenly”, step by step

suddenly traces back through two separate lines of ancestry.

via English sudden

StepLanguageWordMeaning
1EnglishsuddenHappening quickly and with little or no warning;...
2Middle EnglishsodeynSudden; happening or developing without buildup...
3Anglo-Normansodeinsudden; quickly with little or no warning
4Old Frenchsodain
5Vulgar Latinsubitanussudden
6Latinsubitāneussudden, unexpected
7Latinsubitusapproached; succeeded; occurred
8LatinsubeoI go under, come under; enter; I go up to,...
9Latinto go, to fare, to move (oneself) (any kind of animate or inanimate motion: walk, ride, sail, fly, etc.)
10Proto-ItalicI go
11Proto-Italicejō
12Proto-Indo-Europeanh₁éytito go, to be going
13Proto-Indo-Europeanh₁ey-to go

via Middle English sodenly

StepLanguageWordMeaning
1Middle EnglishsodenlyAlternative form of sodeynly

Words derived from “suddenly

Every word from Proto-Indo-European h₁ey-
suddenly — Etymology, Origin & Word History | Etymology Explorer