All I know is that left-handed people were considered sinister and untrustworthy hence the use of the word in modern language as sinister was the word for left.

Certainly in medieval times the assumption was that all arms would be bourne in the right hand. Hence the term right-hand man, meaning the man I trust to guard my exposed right. Also all castles were built with stairs which spiralled anti-clockwise as this favoured the defenders.

This has been the case until quick recently, in fact my mother told me that at school she was forced to write with her right hand and use her knife and fork right-handed and was punished if she was caught doing otherwise.