1911 Encyclopædia Britannica/Vade-mecum

VADE-MECUM, a Latin phrase meaning literally “come with me” (vade, imperative of vadere, to go or come; cum, with; me, abl. of ego, I), and used in French, Spanish and English for something that a person is in the habit of constantly taking about with him, especially a book of the nature of a handy guide or work of reference.