means The power to shape someone's thoughts, choices, or actions—often without force, and often without their noticing.

from From Latin influere, "to flow in" (in-, "in" + fluere, "to flow"), passing through Medieval Latin influentia into English. The word once carried a literal astrological charge: medieval thinkers believed an ethereal fluid streamed down from the stars and planets, flowing into our characters and fates. So "influence" began as starlight pouring into the soul—and only later cooled into the everyday sense of one person quietly flowing into another's mind. (The same fluere current carries fluent, fluid, and flux.)