Today is called O Sapientia, from the Latin for O Wisdom. It is the first of what are called the Advent Antiphons, the special refrains used with the Magnificat at evening prayer (vespers) from today until the 23rd. 

O Wisdom, coming forth from the mouth of the Most High, reaching from one end to the other mightily, and sweetly ordering all things: Come and teach us the way of prudence. cf Ecclesiasticus 24.3; Wisdom 8.1