Dictionary:

prothesis

  (prŏth'ĭ-sĭs)

1. Linguistics. The addition of a phoneme or syllable at the beginning of a word, as in Spanish espina, “thorn,” from Latin spina.
2. Eastern Orthodox Church.
   1. The preparation of the bread and wine for the Eucharist.
   2. The table used for this preparation.

[Greek, prefixing, from protithenai, prothe-, to put before : pro-, before; see pro–² + tithenai, to put.]

In a Greek church, a chapel beside the sanctuary, usually on the north side of the bema.