"What duh hell-" is another way of saying "What the hell", just more exaggerated as the
L'
s in "hell" are usually spammed.
"What duh hell" originates from a
TikTok video of a person going up to strangers and reviewing their
shoes, with them typically being off-brand.
The joke itself is meant to be an "over exaggerated" reaction to what is an off-brand version of a shoe brand, typically being Jordans.
The sentance is usually used as a response to something
weird. The meme is also commonly used as a background audio in videos that are similar to shit post videos.