means The state of being awake and alert rather than asleep or drowsy.

from Built from the Old English word "wacian," meaning to be awake or to watch — the same root that gives us "watch" and "wake." Add the suffix "-ful" (full of) and "-ness" (the state of), and you get a tidy stack: the condition of being full of wakefulness. The "wak-" root traces back through Germanic to a Proto-Indo-European source possibly meaning "to be lively or vigorous," which is also thought to be a distant cousin of Latin "vigil" (watchful) — so to be wakeful and to keep vigil share old, attentive blood.