Cold hands warm heart

I have heard and said this phrase so often...and was asked what exactly does it mean and where did it come from.
I always used it as a reason to explain my cold hands and generous nature. I would like, however, to find out if anyone knows the answers to my questions. Please help!!

COLD HANDS, WARM HEART - "A reserved, cool exterior may disguise a kind heart. The proverb has been traced back to 'Collectanea by V.S. Lean. First cited in the United States in 'Blue Murder' by E. Snell." From Random House Dictionary of Popular Proverbs and Sayings by Gregory Y. Titelman (Random House, New York, 1996).