[1.] [OED:] acute, adj. [=] A. adj. 1. Med.
a. Of a disease, symptom, etc.: coming quickly to a crisis or conclusion; of rapid onset and short duration; of recent or sudden onset; contrasted with chronic adj. 2a; cf. subacute adj. 2.
In similar contexts: severe; critical. Also in figurative context.
[2.] Etymology: < classical Latin acūtus [=] sharpened, pointed, sharp, tapering, having sharp needles, keen, discriminating, keen-witted, shrewd, nimble, quick, pungent, acrid, high-pitched, piercing, shrill, treble, ...
[3.] [Etymonline:] late 14c., originally of fevers and diseases, "coming and going quickly"
(opposed to a chronic), from Latin acutus "sharp, pointed," figuratively "shrill, penetrating; intelligent, cunning," past participle of acuere "sharpen" (see acuity). ...
How did the Latin acuere "sharpen" evolve into definition [1.] above for 'acute'?
Sharpness can be quick or long. So how does sharpen connect with quick?
I am confused because OED states this definition for quickness for the Latin acūtus, but Etymonline doesn't broach quickness until the later reference to fevers and diseases.
Footnote: I read this other post on 'acute'.