'Shadow' and 'shade' are one Old English word split by grammar — 'sceadu' divided by case form.
A dark area or shape produced by a body coming between rays of light and a surface; an inseparable attendant or companion.
From Old English 'sceadw,' 'sceadu' (shadow, shade, darkness, shelter), from Proto-Germanic *skadwaz (shadow), from PIE *skot- (darkness, shadow). The Old English word had an oblique form 'sceadwe' that developed into 'shadow,' while the nominative 'sceadu' became 'shade' — so 'shade' and 'shadow' are the same word, split by grammatical case. The same root produced
'Shadow' and 'shade' are the same Old English word split in two by grammar. Old English 'sceadu' (nominative case) became 'shade,' while its oblique form 'sceadwe' became 'shadow.' One word, two grammatical cases, two modern English words — each with its own nuances, connotations, and metaphorical life.