The story
An orthographic device that forces the preceding vowel to be read ‘short’: ⟨dih⟩ /dɪ/, ⟨bruh⟩ /bɹʌ/, etc. (not */da͡ɪ, bɹu/). Although the letter h has long been used ad-hoc for this purpose in English — see uh and meh — the practice of clipping content words to humorous effect took off as an Internet meme in 2025 and created a productive association between -h and such clippings.
Etymology from Wiktionary, CC BY-SA 4.0.