Acrostic Poems and the Hidden Structures in Text We Overlook

In the first chapter of the Old Testament book of Lamentations, every stanza begins with a successive letter of the Hebrew alphabet. Psalm 119 does the same thing across 176 verses -- eight verses for each of the 22 Hebrew letters. These are acrostic poems, and they've been used for thousands of years as mnemonic devices, literary flourishes, and occasionally, as hidden messages. An acrostic is structurally simple: the first letter of each line (or stanza, or paragraph) spells out a word or phrase when read vertically. But that simplicity belies a genuinely interesting constraint-satisfaction problem that intersects with natural language processing, creative writing, and computational linguistics. The constraint problem Writing an acrostic poem by hand is an exercise in constrained creativity. Say you want to write an acrostic for the word "CODE." You need four lines. The first must start with C, the second with O, the third with D, the fourth with E. Those lines also need to make sens