incredibly
AmericanUsage
Incredibly and, somewhat less commonly, incredulously can both be used to mean “unbelievably,” as in It was an incredulously/incredibly expensive flight. They both share the roots of in, meaning “not,” and crēdere, meaning “to believe,” so this shared meaning of “not able to be believed” is rooted in their etymology. Beware, however: they both also have other senses that are not synonyms. Incredibly can mean “very” or “extremely,” but incredulously is not used that way: This is an incredibly exciting moment for me. Incredulously can mean “disbelievingly,” but incredibly is not used that way: She stared at the painting incredulously, skeptical of its veracity .
Etymology
Origin of incredibly
First recorded in 1500–10; incredib(le) ( def. ) + -ly ( def. )
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.