IPA: /ˈlɪv.lɔŋ/
KK: /ˈlɪvˌlɔŋ/
Entire or whole, often used to describe a duration of time, such as a day.
She worked the livelong day without taking a break.
Livelong → It is formed from "live" (from Old English "libban", meaning to be alive) and "long" (from Old English "lang", meaning of great duration). The word "livelong" means lasting for a long time in life or throughout one's life.
Think of 'living' ('live') for a 'long' time — that's what livelong means.