Greek, 16th century
A book containing essential information on a subject. The ancient Greek ἐγχειρίδιος means “fitting in the hand”. An “enchiridion” came into English in the 16th century as a portable, hand-sized guidebook. The modern handbook has its roots in the enchiridion (related to the Greek word for “hand”), traditionally a small, portable manual widely used from early Greece through to the 19th century. Enchiridons were designed to keep useful information near at hand, including religious teachings, ethical advice, the rules of poetry, guidance for soldiers, and means of understanding the law.
Example: My decades of personal journals comprise an enchiridion of my ambitions, hopes and fears.