Why did Moses stammer? and, was Moses left-handed?

Moses, the great lawgiver, '... the chief of the prophets' according to Maimonides, probably had a speech defect. 'I am not a man of words ... for I am of slow speech, and of a slow tongue', Moses states, and later he pleads '... I am of uncircumsized lips, and how shall Pharaoh hearken unto me'. Most authorities consider these quotations to mean that he stammered.