IPA: //ˈkuːlər//
KK: /ˈkulər/
A container or device used to keep drinks or food cold, often used for picnics or outdoor activities.
We packed the cooler with sandwiches and drinks for our beach trip.
Cooler → The word is formed from "cool" (from Old English *col*, meaning moderately cold) and the suffix "-er" (meaning one who or that which). A cooler is something that makes things moderately cold or a device used to keep items cool.
Think of something that makes things 'moderately cold' — 'cool' means not warm, and '-er' indicates it is a device that does this.