The Collaborative International Dictionary of English v.0.48:

Obvention \Ob*ven"tion\, n. [L. obvention, fr. obvenire to come
   before or in the way of, to befall; ob (see Ob-) + venire
   to come: cf. F. obvention.]
   The act of happening incidentally; that which happens
   casually; an incidental advantage; an occasional offering.
   [Obs.] "Tithes and other obventions." --Spenser.
   [1913 Webster]

         Legacies bequeathed by the deaths of princes and great
         persons, and other casualities and obventions.
                                                  --Fuller.
   [1913 Webster]