Noah Webster
Left
LEFT, preterit tense and participle passive of leave.
LEFT, adjective [Latin lavus; Gr. probably from the root of leave, Gr. and properly weak, deficient. Applied to the hand or arm, it denotes the weak arm, as opposed to the right, the strong or dextrous. Hence the ancient idea of sinister, unfortunate, attached to the left arm or side.]
1. Denoting the part opposed to the right of the body; as the left hand, arm or side. Hence, the noun being omitted, we say, on the left that is, on the left side or wing, as of an army.
2. The left bank of a river, is that which is on the left hand of a person whose face is towards the mouth of the river.