1831, "act of becoming specialized," noun of action from specialize. Biological sense from 1862. In science and scientific education, "a direction of time and energies in one particular channel to the exclusion of others," by 1880.
If you peruse the people in the news
The people that the magazines refer to
You'll find that they are naturally soignée
The special ones that all of us defer to
They've each a trait that seems to state first raters
That separates them from the small potaters
["Specialization," lyrics by Sammy Cahn]