The Collaborative International Dictionary of English v.0.48:

Interplead \In`ter*plead"\, v. i. (Law)
   To plead against each other, or go to trial between
   themselves, as the claimants in an in an interpleader. See
   Interpleader. [Written also enterplead.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Enterplead \En`ter*plead"\, v. i.
   Same as Interplead.
   [1913 Webster]