late 14c., "act of bringing together and comparing," from Old French collation (13c.) "collation, comparison, discussion" (also "a light supper"), from Latin collationem (nominative collatio) "a bringing together, collection, comparison," noun of action from collatus, irregular past participle of conferre "to bring together" (see collate).
The word has had many meanings over the centuries in theology and law. It was the title of a popular 5c. religious work by John Cassian (sometimes translated into Old English as Þurhtogenes), hence the word's general sense "a compilation of lives of the Church fathers." The "light supper" sense is from the meal taken by members of a monastery at the end of the day after hearing readings from the Collation.