I know of no better way of conveying the sense of the original σκαῖος than by thus introducing the Latin sinister, which has the double meaning of left and ill-omened.  It is to the credit of the unsuperstitious character of English speaking people that while the Greek σκαῖος and ἀριστερός, the Latin sinister and lævus, the French gauche, and the German link, all have the meaning of awkward and unlucky as well as simply on the left hand, the English left (though probably derived from lift=weak) has lost all connotation but the local one.