Full Idea
Locke's distinction between real and nominal essences appears to be in reference to the Aristotelian distinction between real and nominal definitions.
Gist of Idea
Locke's real and nominal essence refers back to Aristotle's real and nominal definitions
Source
report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.06.02) by Jan-Erik Jones - Real Essence §2
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.4
A Reaction
A revealing observation. Locke's philosophy is thoroughly Aristotelian in character, but with the addition of an empirical scepticism that blocks the more speculative (and explanatory) aspects of Aristotle.