As mentioned in Categories for the Working Mathematician, Bourbaki nearly had the right definition of an adjunction 10-15 years before the proper definition was formulated by Dan Kan. In fact, Bourbaki actually proved the Special Adjoint functor theorem (cf. Categories for the Working Mathematician - notes at the end of the chapter on Adjunctions)

As mentioned in Categories for the Working Mathematician, Bourbaki nearly had the right definition of an adjunction 10-15 years before the proper definition was formulated by Dan Kan. In fact, Bourbaki actually proved the Special Adjoint functor theorem (cf. Categories for the Working Mathematician - notes at the end of the chapter on Adjunctions)

Edit: To explain a little more (from Mac Lane), Bourbaki had figured out most of these notions, but since they had not formulated the general adjoint functor theorem, only the special adjoint functor theorem, they restricted their definition of a "universal construction" to those adjunctions for which the SAFT holds. I find it pretty impressive that they were able to do all of this without the benefit of a formal framework for category theory.