Stupidity

All The Stupid People, 

Where DO They All Get Off...?

stupid (adj.)

1540s, "mentally slow, lacking ordinary activity of mind, dull, inane," from Middle French stupide (16c.) and directly from Latin stupidus "amazed, confounded; dull, foolish," literally "struck senseless”, rom stupere "be stunned, amazed, confounded," from PIE *stupe- "hit," from root *(s)teu- (1) "to push, stick, knock, beat" (see steep (adj.)). 

Related: Stupidly; stupidness.