libretto

The word 'libretto' entered English directly from Italian in the mid-18th century, retaining its original meaning of "a small book." Its Italian source, 'libretto', is a diminutive of 'libro' (book), which itself descends from the Latin 'liber'. In Latin, 'liber' originally referred to the inner bark of a tree, a material used for writing before the advent of paper. This etymological journey—from tree bark to book to the specialized text for a musical drama—perfectly illustrates the word's conceptual core: it is the essential written text, the "little book," upon which the grand spectacle of an opera is built.

This word is a direct loan from Italian and is not productively segmented using English morphemes. In its source language, it is the diminutive form of 'libro' (book), from Latin 'liber' (book, inner bark of a tree).