Back to explorer

entry

obtuse

/əbˈtuːs/

Blunt, dull, or slow to perceive

From Latin ob (against) + Latin tund (to beat).

adjective
verb
ob
Latin
AI-inferred
ob
a prefix meaning 'against' or 'toward'
Latin
Verified
obtusus
literally 'beaten against, blunted'

from Latin obtusus "blunted, dull," also used figuratively, past participle of obtundere "to beat against, make dull,"

tund
Latin
AI-inferred
tundere
to beat, strike, knock
Latin
AI-inferred
obtundere
to beat against; to dull or blunt
Latin
Verified
obtusus
past participle: 'blunted, dull'

from Latin obtusus "blunted, dull," also used figuratively, past participle of obtundere "to beat against, make dull,"

Combined
obtusus
the prefix ob- joins tundere to create the sense of something beaten down and made dull
Middle English
AI-inferred
obtuse
borrowed in the early 15th century with the sense 'dull, blunted'
Early Modern English
AI-inferred
obtuse
extended to 'stupid, not perceptive' and then to geometry
Modern English
obtuse

A blunt object can become a blunt idea, and Latin was happy to make that leap. The Romans had ob-, a prefix for being pressed against something, and tundere, “to beat” — the same hard-hitting family that gives us obtund, contuse, and the whole business of being thumped into dullness. Put them together and you get obtusus, something literally “beaten down” or “blunted,” which English borrowed in the early 1400s. By around 1500, people were using it for a person whose mind seemed just as unsharpened as a worn-down blade. Then geometry got hold of it in the 1560s and turned insult into mathematics: an obtuse angle is simply one that refuses to stay right. Tomorrow, you can remember it as the word for anything that has been battered past the point of sharpness — metal, sound, or brain.

§