An Etymological Dictionary of Astronomy and Astrophysics

An angle whose measure is greater than 90° and less than 180°.

Etymology (EN): Obtuse, from M.Fr. obtus (fem. obtuse), from L. obtusus “blunted, dull,” p.p. of obtundere “to beat against, make dull,” from ob “against” + tundere “to beat,” from PIE *(s)tud- “to beat, strike, push, thrust;” → angle.

Etymology (PE): Zâviyé, → angle; bâz “open,” from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.] “away, from;” Av. apa- [pref.] “away, from,”
apaš [adv.] “toward the back;” cf. Skt. ápāñc “situated behind.”