From Old English 'laetan' (to allow, release), from PIE *leh1d- (to let go) — permission through non-interference.
To allow or permit something to happen; to not prevent or forbid.
From Old English 'lǣtan' meaning 'to allow, permit, cause, let go, leave behind, bequeath,' from Proto-Germanic *lētaną (to let, leave, allow), from PIE root *leh₁d- (to let, leave, be weary, slack). The original sense combined 'allowing' with 'leaving alone' — to let was to release one's hold or control over something, to make slack what had been taut. This passive concept of permission through
English has two completely unrelated words spelled 'let': one meaning 'allow' (from Old English 'lǣtan') and one meaning 'hinder' (from Old English 'lettan'). The 'hinder' sense is nearly extinct but survives in tennis: a 'let' serve is one obstructed by the net, and in legal English 'without let or hindrance' means without obstruction. The two words are