I'm imagining a knife. Not very sharp = dull, right? Is that the origin of the use of "obtuse" to mean "not very bright"?

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    Obtuse means 'dull', physically; it comes from the Latin verb obtundere, which means 'to beat against' something, i.e, to dull it. Dull itself, however, has a different etymology, coming through Proto-Germanic *dul-, ablaut-form of *dwel- 'to be foolish', and ultimately to P.I.E. *dheu¹-, which refers to a number of things, including "defective perception or wits". So dull is not only unrelated to obtuse etymologically; it turns out that the physical meaning 'not sharp' is derived from the original meaning 'stupid'. Some metaphors are older than I thought. Nov 2, 2013 at 23:10
  • Your explanation is great, @JohnLawler, you should put this into an answer.
    – Safira
    Nov 2, 2013 at 23:33
  • Yes, fascinating answer, I'd love to "accept" it. Nov 4, 2013 at 4:28

2 Answers 2


English has long associated terms for wit and weapons, beginning with sharp in Old English:

Old English scearp “having a cutting edge; pointed; intellectually acute, active, shrewd; keen (of senses); severe; biting, bitter (of tastes),” from Proto-Germanic *skarpaz, literally “cutting”. . . . The figurative meaning “acute or penetrating in intellect or perception” was in Old English. . . .

It appears that a similar figurative usage influenced the meaning of obtuse (both in English and its source languages):

early 15c., “dull, blunted,” from Middle French obtus (fem. obtuse), from Latin obtusus “blunted, dull,” also used figuratively. . . . Sense of “stupid” is first found c.1500.

Conversely, dull “stupid” (from Old English dol “dull-witted, foolish”), blunt (perhaps related to blunder), and keen “clever, wise” (from Proto-Germanic *kan-) developed in the other direction, referring first to wits c.1200 and later becoming associated with weapons and tools in the 13–14c.

Thus, while these words are unrelated etymologically, the wit/weapon metaphor has influenced them all to describe both physical and mental edges in English.


I note in usage that obtuse tends toward the meaning of "(intentionally) stupid", as in the admonishing "Don't be obtuse!" (when someone is obviously, obstinately, pretending ignorance.)

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    Hi, and welcome to English Language & Usage. You might improve your answer by citing references. And do you see ways in which the word "dull" is related to "obtuse"?
    – rajah9
    Feb 7, 2020 at 18:19

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