The word "withering" comes from the verb "wither", which evolved from Middle English widderen ("to dry up, shrivel"), possibly an alteration of wederen ("to expose to weather"), linking it to the word "weather".   It ultimately stems from Old English wiþerian, meaning "to resist" or "struggle against," and Proto-Germanic roots meaning "against" or "separate," suggesting a core sense of drying out or being worn down by conditions. 

According to the Oxford English Dictionary (OED), the adjective "withering" was first used in English in the late 1500s, with the earliest evidence found in the writings of E.K. in 1579. The word is formed within English from the verb "wither" and the "-ing" suffix.  "Withered" (adjective) appeared earlier (1488), while the adverb "witheringly" appeared later (1815).

Examples of "withering" first used in English: 
"She is a patient one, and dismissed me with a withering glance." 
"Grandmother’s withering hands were once strong but have now shriveled up to almost nothing." 
 "The scorching summer sun caused the withering grass to become brown and limp."  
"His head tender with such thoughts, he trod through the withering blossoms to the Mission." 
"The daily firings produced by the withering economy offered loopholes of opportunity for a young man who kept his eyes open." 
"The ideology of inclusion is withering away, to be replaced by a revival of survival-of-the-fittest capitalism." 

And as long as @drpaladin mentioned withers: 

The term withers derives from Old English wither ("against'), because the withers are the part of a draft animal that pushes against a load.

Just the facts:

WITHERING Definition & Meaning - Merriam-Webster

WITHERING Synonyms: 69 Similar and Opposite Words | Merriam-Webster Thesaurus

7 minutes ago, Bill W said:

And as long as @drpaladin mentioned withers: 

The term withers derives from Old English wither ("against'), because the withers are the part of a draft animal that pushes against a load.

Kudos to you, thwarted once more! I was about to post on this same comment, as you. What a difference a simple 's' can make.

WITHERS Definition & Meaning - Merriam-Webster