encyclopedia

English encyclopedia comes from New Latin encyclopaedīa, a fused form of the Koine Greek phrase enkúklios paideíā, literally 'education in the circle of arts and sciences.' That phrase joined enkúklios, meaning 'circular,' with paideíā, meaning 'childrearing' or 'education.'

What started as a Greek description of a well-rounded education — learning arranged in a full circle of subjects — was later univerbated into a single Latin word and borrowed into English as the name for the book itself.

Paideíā, the 'education' half of the phrase, is built from paîs, meaning 'child' — the same root sense behind the idea of childrearing at the heart of the word.