Full Idea
P is 'extraneously essential' to x iff it is possessed by x at any world w only in virtue of the possession at w of certain properties by other objects.
Gist of Idea
A property is 'extraneously essential' if it is had only because of the properties of other objects
Source
Graeme Forbes (In Defense of Absolute Essentialism [1986], 2)
Book Reference
'Midwest Studs XI:Essentialism', ed/tr. French,Uehling,Wettstein [Minnesota 1986], p.4
A Reaction
I would say that these are the sorts of properties which have nothing to do with being essential, even if they are deemed to be necessary.
Related Idea
Idea 13806 Trivially essential properties are existence, self-identity, and de dicto necessities [Forbes,G]