mortmain

1. Law. Perpetual ownership of real estate by institutions such as churches that cannot transfer or sell it.
2. The often oppressive influence of the past on the present.

[Middle English mortemayne, from Old French mortemain : morte, feminine of mort, dead; see mortgage + main, hand (from Latin manus).]

[French, Dead hand.] A term to denote the conveyance of ownership of land or tenements to any corporation, religious or secular.

Traditionally, such transfers were made to religious corporations. Like any corporation, the religious society had unlimited, perpetual duration under the law. It could, therefore, hold land permanently unlike a natural person, whose property is redistributed upon his or her death. The holdings of religious corporations grew as contributions were received from their members. Because such holdings were immune from responsibilities for taxes and payment of feudal dues, greater burdens were placed on noncorporate secular property. Therefore, land in mortmain was said to be held in perpetuity in one dead hand, that of the corporation.

The noun has 2 meanings:

Meaning #1: real property held inalienably (as by an ecclesiastical corporation)
  Synonym: dead hand

Meaning #2: the oppressive influence of past events of decisions
  Synonyms: dead hand, dead hand of the past