An octonary is an eight-line section in a poem, song or psalm. The most notable example is found in Psalm 119
In the French renaissance the octonaire became a form of moralizing chanson.
It can also mean of 8th rank or order (primary, secondary, tertiary … octonary).
References
↑Merriam-Webster's encyclopedia of literature 1995 p825 "octonary \'ak-ta-,ner-e \ In poetry, a stanza or group of eight verses;"
↑Calvin Bible Commentaries: Psalms, Part IV p287 "Some call this the octonary psalm, because that, through every successive eight verses, the initial words of each line begin with the same letter in alphabetical order."