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late 14c., of persons; 1650s of tools, etc., from left (adj.) + handed. In 15c. it also could mean "maimed." Sense of "underhanded" is from early 17c., as in left-handed compliment (1787, also attested 1855 in pugilism slang for "a punch with the left fist"), as is that of "illicit" (e.g. left-handed marriage). Related: Left-handedly; left-handedness.
Using the left hand more skillfully or easily than the right.
(Judg. 3:15; 20:16), one unable to use the right hand skilfully, and who therefore uses the left; and also one who uses the left as well as the right, ambidexter. Such a condition of the hands is due to physical causes. This quality was common apparently in the tribe of Benjamin.