acer

From Latin ācer / ācris 'sharp, pointed, pungent, keen,' with the related verb acuere 'to sharpen' and noun acus 'needle.' The same idea of a sharp point runs through physical edges, biting smells, sour tastes, and a quick mind. English variants include acr- (acrid, acrimony), acu- (acupuncture, acumen), and acid (sour = sharp on the tongue).