EWTN Catholic Q&A
Blessing with Left Hand
Question from lroy on 10-20-2013:

Not everybody has a right arm, let alone a hand. Some right hands are deformed or have serious injuries. Allowances should be made for these people.

I wonder if this is part of back when people were not allowed to write with the left hand (the "devil's hand").

Answer by Richard Geraghty on 10-20-2013:

Dear Lroy,

Allowances are made for such people. The Church does not demand the impossible. An interesting point to note is that the words "sinister" and "dexterous" are derived from the Latin for left and right. In olden days men wore their sword on their left side because it was easier to draw by the right hand. Since most men were right handed (they still are) they were quite aware of when men has their swords.

Dr. Geraghty