re

The word 're' has a dual origin, both stemming from Latin. Its musical meaning began in the 11th century with Guido d'Arezzo's system for teaching sight-singing. He took the initial syllables from each half-line of a Latin hymn to St. John the Baptist, with 're' deriving from 'resonare' ('to resound'), to create the solfège sequence 'ut, re, mi, fa, sol, la'. Its use as a preposition, meaning 'in the matter of', entered English legal and business language directly from Latin, where 'in re' meant 'in the thing' or 'in the case of'. This legal shorthand was eventually shortened to the standalone 're' to introduce a subject heading. Thus, a single syllable connects the abstract world of legal matters to the foundational notes of Western music.

This is a simplex word. It originates from the Latin syllable used in the Guidonian solmization system, which itself was taken from the first syllable of the Latin word 'resonare', meaning 'to resound'. As a preposition, it is a direct borrowing from the Latin ablative case of 'res', meaning 'thing' or 'matter'.