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Vine's Expository Dictionary of NT Words [1]

1: Ἀριστερός (Strong'S #710 — Adjective — aristeros — ar-is-ter-os' )

is used (a) of the "left" hand, in  Matthew 6:3 , the word "hand" being understood; in connection with the armor of righteousness, in  2—Corinthians 6:7 , "(on the right hand and) on the left," lit., "(of the weapons ... the right and) the left;" (b) in the phrase "on the left," formed by ex (for ek), "from," and the genitive plural of this adjective,  Mark 10:37 (some mss. have No. 2 here);   Luke 23:33 .

2: Εὐώνυμος (Strong'S #2176 — Adjective — euonumos — yoo-o'-noo-mos )

lit., "of good name," or "omen" (eu, "well," onoma, "a name"), a word adopted to avoid the ill-omen attaching to the "left" (omens from the "left" being unlucky, but a good name being desired for them, cp. aristeros, lit., "better of two," euphemistic for the ill-omened laios and skaios; cp., too, the Eng., "sinister," from the Latin word meaning "left"), is used euphemistically for No. 1, either (a) simply as an adjective in  Revelation 10:2 , of the "left" foot; in  Acts 21:3 , "on the left" (lit., "left"); or (b) with the preposition ex (for ek), signifying "on the left hand,"  Matthew 20:21,23;  25:33,41;  27:38;  Mark 10:40 (for ver. 37, in some mss., see No. 1); 15:27.

Webster's Dictionary [2]

(1): ( imp. & p. p.) of Leave

(2): ( a.) Situated so that the left side of the body is toward it; as, the left side of a deliberative meeting is that to the left of the presiding officer; the left wing of an army is that to the left of the center to one facing an enemy.

(3): ( imp. & p. p.) of Leave.

(4): ( a.) Of or pertaining to that side of the body in man on which the muscular action of the limbs is usually weaker than on the other side; - opposed to right, when used in reference to a part of the body; as, the left hand, or arm; the left ear. Also said of the corresponding side of the lower animals.

(5): ( n.) That part of surrounding space toward which the left side of one's body is turned; as, the house is on the left when you face North.

(6): ( n.) Those members of a legislative assembly (as in France) who are in the opposition; the advanced republicans and extreme radicals. They have their seats at the left-hand side of the presiding officer. See Center, and Right.

King James Dictionary [3]

LEFT, pret. and pp. of leave.

LEFT, a. L. 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.

International Standard Bible Encyclopedia [4]

left ( שמאל , sāma'l , "to go to the left," "to turn to the left," שׂמאול , שׂמאל , semō'l , "the left hand," שׂמאלי , semā'lı̄ , "belonging to the left," "situated on the left"; ἀριστερός , aristerós , and euphemistically εὐώνυμος , euṓnumos , literally, "having a good name," "of good omen"): The words are chiefly used in orientation with or without the addition of the word "hand." So Abraham says to Lot: "If thou wilt take the left hand ( semō'l ), then I will go to the right; or if thou take the right hand, then I will go to the left ( sāma'l )" (  Genesis 13:9 ). Frequently in Hebrew idiom the right hand and the left are mentioned together in order to express the idea "everywhere," "anywhere," "altogether" ( Genesis 24:49;  Exodus 14:22 ,  Exodus 14:29;  Numbers 22:26;  Deuteronomy 2:27;  Deuteronomy 5:32;  2 Corinthians 6:7 ). In the geographical sense the left is synonymous with north ( Genesis 14:15;  Joshua 19:27;  Ezekiel 16:46;  Acts 21:3 ). While the left hand is considered as weaker than the right (see Lefthanded ), it is the hand which holds the bow ( Ezekiel 39:3 ). The left hand is the side from which bad omens come, and therefore less lucky and less honored than the right hand (see Hand , note).

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [5]

(prop. שְׂמאֹול , Sem '''''Ô''''' L ´ . a primitive word; Gr. Εὐώνυμος ', lit. Well-Named, i.e. lucky, by euphemism for Ptar Ἀριστερός , as opposed to יָמַין , Δεξιός , the right). The left hand, like the Latin Laevus, was esteemed of ill omen, hence the term Sinister as equivalent to unfortunate. This was especially the case among the superstitious Greeks and Romans (see Potter's Gr. Ant. 1:323. Adams, Romans Ant. p. 301). Among the Hebrews the left likewise indicated the north ( Job 23:9;  Genesis 14:15), the person's face being supposed to be turned towards the east. In all these respects it was precisely the opposite of the Right (q.v.).