In the modern meaning of “sinister but adroit or dexterous”, there is nothing wrong, beyond the fact that wicked persons who are also clever should possibly be avoided. For lexicographers and others who remember their Latin, however, the question brings a snort and a smile or frown.
Sinister and dexterous come directly from Latin. Adroit also comes from Latin, but via French. Sinister in Latin means the left side. Dexter means the right side. Adroit is French, from Latin directus (straight): à droit, to the right.
No wonder the lexicographers would smile or frown at the question: a person cannot logically be described as being both left and right. To use another word from French: a person cannot be both adroit and gauche, which means “left” in French.
But in English, sinister and dexterous/adroit have other meanings. Sinister and dexter also did in classical Rome, the same ones we connect with the English words. Sinister was improper, adverse, inauspicious. Dexter meant skillful, favorable, fortunate, opportune.
It is a right-handed world, and probably always has been. In Chinese and other eastern languages, the same associations occur: right is good, left is bad. That doesn't have to apply to the character of left-handed persons, but it has sometimes been projected on to them by the (approximately) 90% majority of right-handers.
Maybe that was just because left-handers were in the minority, but perhaps because in combat and sports they were unco
mfortable adversaries, bearing their sword in the hand that a right-hander could not fend off with his shield. Of course, the left-hander had the same problem, but had grown up with it and was more adroit at dealing with the disadvantage. Left-handers had to adapt to eat with their right hand from the common pot (“cack-handed” is one derogatory slang expression for left-handers). They were forced to learn to write with their right hand.
Left-handers don't need to be reminded of all the items that are designed for right-handers, starting with scissors as a child and continuing with virtually everything else. Rulers are made for right-handers to trace a line from zero on the left to whatever length they want to measure. Cameras, firearms, can-openers are made for right-handers, even simple screws: easier to tighten with a twist of the right hand. Maybe even the way certain items of women's underwear hook together is more convenient for right-handed persons—the wearer, of course.
The English words left and right as used for directions have different roots, coming from Old English, but with similar connotations. Left is from the Old English lyft: weak, foolish; later taking the present meaning. Right, from the Old English riht, originally meant only good, proper, correct, going back to Latin rectus, straight, correct. So there is still the same feeling that right is good, strong, proper; while left is inferior in comparison. In French, gauche also had the meaning of awkward, awry, before it took on the meaning of “left”, replacing senestre.
Of course, right-handers also have a left hand, that is weaker and less dexterous.
Luckily, under the laws of most countries, left-handers have the same rights as the majority—but they will still be asked to use their right hand to swear an oath.
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