abecedarius

Its 23 verses each begin with a consecutive letter of the alphabet, making the poem an abecedarius.

An abecedarius is an acrostic in which the first letter of every word, strophe or verse follows the order of the alphabet.

Relatively simple acrostics may merely spell out the letters of the alphabet in order; such an acrostic may be called an 'alphabetical acrostic' or Abecedarius.

The Biblical psalmist undoubtedly used the combination of the verse form and an abecedarius to remember Psalm 119, each of whose twenty-two octaves begins with a successive letter of the Hebrew alphabet.