Apparently the meaning doesn't come from the verb but from the italian word : "compositore" (according to wikitionary [1] and the larousse dictionary [2])

(again in [1]) "compositore" from italian is equivalent to "compositeur" in french which can mean "a person that writes music" but can also mean "a typographer or compositor".

[1] : https://fr.wiktionary.org/wiki/composteur

[2] : https://www.larousse.fr/dictionnaires/francais/composteur/17...