What is the context for using the term "bones" to refer to someone. I have seen that in the original "Star Trek", Kirk calls Dr. McCoy as "bones" and this word was translated to portuguese, my natural language, as "magro", that means "thin"... and I am not sure if this is the correct translation. I have also seen this word being used on the TV Series "Bones" with a different context.
Bones in this context is derived from sawbones, slang for a physician or surgeon.
Before anaesthetics (and antibiotics) were invented, surgery was often rudimentary for fairly obvious reasons. The reputation of a surgeon tended to be based on how quickly he could perform an amputation (I say "he" advisedly since there were no female surgeons at the time.) This involved little more than making the patient as drunk as possible to dull the pain, getting several assistants to hold him (or her) down, and then sawing through the affected limb as quickly as possible to minimise the agony caused. Robert Liston, a noted Victorian surgeon, was said to be able to amputate a leg in two and a half minutes, and once removed a limb in 28 seconds.
For this reason, as has already been said, surgeons and doctors were often called sawbones, and a good one was quick as well as accurate. Doctors were also known as quacks, but this term would have been a gross insult to any surgeon.
Usually a shortened version of the slang term "sawbones" which referred to the original surgeons of medicine because they used saws to remove damages limbs from patients. A good 'sawbones' could remove a limb in seconds using a hacksaw, alcohol and some strong assisents to hold the patient down.