word-forming element in legal English (and in imitation of it), representing the Anglo-French -é ending of past participles used as nouns (compare -y (3)). As these sometimes were coupled with agent nouns in -or, the two suffixes came to be used as a pair to denote the initiator and the recipient of an action.
Not to be confused with the French -ée that is a feminine noun ending (as in fiancée), which is from Latin -ata.
Such a word as trusteeship is eminently characteristic of the composite character of the language: Scandinavian trust + a French ending used in a manner unparalleled in French + an Old English ending. [Otto Jespersen, "Growth and Structure of the English Language"]
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Definitions of trustee from WordNet
a person (or institution) to whom legal title to property is entrusted to use for another's benefit;