acumen (n.) Look up acumen at Dictionary.com
"quickness of perception, keen insight," 1530s, from Latin acumen "a point, sting," hence, figuratively, "mental sharpness, shrewdness," from acuere "to sharpen," literal and figurative (of intellect, emotion, etc.), related to acus "a needle," from PIE root *ak- "rise to a point, be sharp" (see acro-). Related: Acuminous.