A widely available thought is not one poet’s distinctive possession. But an uncommon image of a quality, in which several elements are combined unexpectedly, has a more individualized character.
Illustrative contrast: “He is brave” is generic. Expressing that courage by an unusual historical image with a particular causal relationship may be a recognizably original expression.
Distinctiveness need not reside in a new word. It can lie in the selected comparison, its contextual cue, or the reasoning that connects an image to the praised quality.