“We can go beyond the dualism expressed by twins to outright binary opposition as one of the underlying structures of Indo-European ideology. The most familiar example can be seen in how the Indo-Europeans treated the basic directions. As we have seen, the opposition between the Proto-Indo-European words for right and left also presents a systematic opposition between the concepts of propitious, healthy, strong, dexterous (Latin dexter, Sanskrit daksina, Avestan dasina-, Lithuanian desine, Old Church Slavonic desn, Greek dexios, Old Irish dess, Albanian djathtë, and so on, from Proto-Indo-European *deḱs-), and the left which is unfavourable, unsound, weak, or, to use the Latin again, sinister. This opposition is also sexual since the right side or right hand is regularly associated with males and the left with females. Furthermore, the opposition also carries into the cardinal directions: the propitious south lay to the right (the Sanskrit and Irish words for right also mean south), while to the left lay the malevolent north, thus demonstrating that Proto-Indo-Europeans faced east to orient themselves. This right—left polarity is naturally not confined to the Indo-Europeans but can be found throughout the world.”
--J.P. Mallory, In Search of the Indo-Europeans: Language, Archaeology, and Myth, ISBN 050005052X, p. 140
Anyone know how sinister (Latin for left) came to mean something bad?
I do! I do!
It comes from fortune telling. When facing North and a flock of ravens take flight towards the setting sun, that means some bad news is a-coming.
That's along the lines of what I read - in Caesar's Gallic Wars, by Julius Caesar, he explains that when an army sets off, seeing an eagle flying on their left (sinister in Latin) was seen as a bad omen. Hence in English, sinister has bad connotations and, as sinister means left, the left also has bad connotations.