The story
Blend of individual + duh. In 1995, Dilbert cartoonist Scott Adams asked readers of the Dilbert Newsletter to come up with a "good derogatory nickname for non-DNRC [Dogbert's New Ruling Class, the official Dilbert fanclub] people" that "should sound harmless and endearing but have a clever double meaning", ultimately selecting "induhvidual" (submitted by "Heather of Beantown") as the winning entry. Issues of the newsletter since then have included a section called "True Tales of Induhviduals" featuring reader-contributed stories about people doing foolish things.
Etymology from Wiktionary, CC BY-SA 4.0.