[Meaning] preparatory teaching.[1]
"And whoever supposes that the Muses are not a preparation, but the power of wisdom is in them for him, and does not wish to understand, if sometimes they hint at something excessive, [...] and is held fast by this [beauty], [...] may many good things come to him."[2]
Marriage is also called a ceremony, and prote/leia are the sacrifices [made] for the sake of the marriage.[3]
"But also let a sacrifice be offered before the wedding of Sinonis and let the husband be the preparation for the seducer."[4]