means The dark shapes cast when an object blocks a source of light, or more loosely the dim, half-hidden places where light barely reaches.

from From Old English 'sceadu,' meaning shade or shadow, with roots tangled in the same Germanic stock that gave us 'shade' itself — the two words are essentially twins that drifted apart, with 'shadow' keeping an extra syllable from the inflected forms. It's possibly related to a Proto-Germanic root '*skadwaz,' and likely a distant cousin of the Greek 'skotos,' meaning darkness.