ˌvādēˈmēkəm, ˌväd- noun
( plural vade mecums )
Etymology: Latin, go with me
1. : a book for ready reference : handbook , manual
his first treatise … became a vade mecum for the local magistrates — V.L.Wilkinson
2. : something regularly carried about by a person
the small wooden bowl, the indispensable vade mecum of all Tartars — William Hazlitt †1893