"Entäußerung ist ein philosophischer Begriff, der vor allem von Hegel geprägt wurde. Er ist verwandt mit dem Begriff der Vergegenständlichung, besitzt aber auch Aspekte des Begriffs der Entfremdung."

I don't normally recommend looking at other people's translations for inspiration, since these things aren't set in stone. But I think it might be a good idea in this case.

It also depends on the context, which you haven't given. In some cases, it might be appropriate to leave it in German, with or without an explanation.



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Note added at 3 hrs (2015-08-18 17:26:56 GMT)
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I didn't read your question properly, but you say it's always left in German. Maybe you should too - it depends who you're writing for.

"Hegel uses two words for ‘alienation’: 1. Entfremdung corresponds to entfremden (‘to make alien’), from fremd (‘alien’). In Middle High German (i.e. from the twelfth to the fifteenth century) it referred to taking or stealing a person's goods and also to mental alienation, especially a coma or stupor. But later it primarily indicated the estrangement of persons from one another. 2. Entäusserung corresponds to entäussern , ‘to make outer or external ( ausser )’, and means ‘surrender’ or ‘divestiture’. (Hegel uses Entäusserung , but not Entfremdung , to refer to the alienation, i.e. voluntary disposal, of one's own property: PR §§65ff.) Other words in the same area are: Entzweiung (from zwei , ‘two’), ‘bifurcation’, ‘disunion’; Zerrissenheit (from zerreissen , ‘to tear, rend, dismember, disconnect’), ‘dismemberment’, ‘disjointedness’; Zwiespalt (also from zwei ), ‘discord’, ‘conflict’, ‘discrepancy’; Diremtion ; and Trennung , ‘separation’ (from trennen , ‘to separate’). Alienation for Hegel is the stage of disunion which emerges from a simple unity and is subsequently reconciled in a higher, differentiated unity. His concept of alienation, though substantially original, owes much to previous thinkers [...]"

In these 2 references, it is translated as "externalization"
https://goo.gl/JHlyq9
https://goo.gl/mNzNtq