Orison \AWR-uh-zuhn\ , noun;
1. A prayer
This word dates to the late 12th century from Anglo-French oreison, which is related to Old French oraison ("oration"). The French words derive from Latin orationem ("speech, oration"), but the modern meaning is provided by the Church Latin definition of orationem: "prayer, appeal to God". Both Latin words are forms of orare, which derives from the Proto-Indo-European base *or- ("to pronounce a ritual formula"). Oration has the same etymology as orison, but it isn't attested until the mid-1400's.
Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Tuesday, June 14
Etymologies come from the Oxford English Dictionary and/or Etymonline.com