The Collaborative International Dictionary of English v.0.48:

Euchologion \Eu`cho*lo"gi*on\, Euchology \Eu*chol"o*gy\, n. [NL.
   euchologion, Gr. ? prayer book; ? prayer, vow (fr. ? to pray)
   + ? to say, speak.] (Eccl.)
   A formulary of prayers; the book of offices in the Greek
   Church, containing the liturgy, sacraments, and forms of
   prayers.
   [1913 Webster]