Where does “credibly” come from?

Credibly derives from Middle English -ly added to Old English -līċ, from Latin credibilis, formed with the suffix -ibilis from the root dʰeh₁- meaning to place or put.

credibly (English): In a credible manner; believably; Used to report...

Definitions

In a credible manner; believably; Used to report...

Ancestry of “credibly”, step by step

Step	Language	Word	Meaning
1	English	credible	Believable or plausible; Authentic or convincing
2	Middle English	credible	—
3	Old French	credible	—
4	Latin	crēdibilis	—
5	Latin	crēdō	—
6	Proto-Italic	krezdō	—
7	Proto-Indo-European	ḱréddʰh₁eti	to believe, trust
8	Proto-Indo-European	-dʰh₁eti	Forms resultative verbs
9	Proto-Indo-European	dʰeh₁-	to do, put, place

Every word from Proto-Indo-European dʰeh₁- →

credibly — Etymology, Origin & Word History | Etymology Explorer