acrostic; telestich; abecedarian hymns

Definition 
Acrostics can be any composition (poems, puzzles, etc.) in which certain letters of the lines, taken in order, form a word, phrase, or sentence that is the subject of the composition. When the last letters of lines do this, the acrostic is sometimes called a telestich (from the Greek tele, "far," and stichos, "row"). Acrostic derives from the Greek akros, "top," and stichos. The term was first applied to the prophecies of the Greek Erythraean sibyl, which were written on separate pages, the initial letters forming a word when the pages were arranged in order. Another famous early acrostic was made from the Greek for "Jesus Christ, God's Son, Savior": Iesus Christos, Theou Uios, Soter. The first letters of each word (and the first two letters of Christos and Theou) taken in order spell ichthus, Greek for "fish," which became a Christian symbol for Jesus. There are even earlier examples of acrostics in the Bible. In Hebrew, for instance, Psalm 119 is an acrostic in which the first letters of each of the 22 stanzas descend in alphabetical order. Such alphabetical acrostics are usually called abecedarian hymns, or abecedarius, and there are more complicated species of them in which each word in every line begins with the same letter:

An Austrian army, awfully array'd
Boldly by battery besieged Belgrade, etc.