The Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 phrase expresses the idea of eternity

Eternity

While in the popular mind, eternity often simply means existence for a limitless amount of time, many have used it to refer to a timeless existence altogether outside time. By contrast, infinite temporal existence is then called sempiternity. Something eternal exists outside time; by contrast,...

. It is biblical, taken from the Vulgate

Vulgate

The Vulgate is a late 4th-century Latin translation of the Bible. It was largely the work of St. Jerome, who was commissioned by Pope Damasus I in 382 to make a revision of the old Latin translations...

 translation of the New Testament

New Testament

The New Testament is the second major division of the Christian biblical canon, the first such division being the much longer Old Testament....

, rendering Greek

Koine Greek

Koine Greek is the universal dialect of the Greek language spoken throughout post-Classical antiquity , developing from the Attic dialect, with admixture of elements especially from Ionic....

 . The usual English translation is "for ever and ever", but in Ephesians 3:21, the KJV notably has "world without end". Neither translation is literal, as the time span invoked is not literally eternity but an in Greek, translated as in Latin, and elevated to "an of " or "a of ". The in Roman antiquity was the potential maximal human lifespan, or roughly a century. The original meaning of was comparable, and it is so used in Homer

Homer

In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

 and Hesiod

Hesiod

Hesiod was a Greek oral poet generally thought by scholars to have been active between 750 and 650 BC, around the same time as Homer. His is the first European poetry in which the poet regards himself as a topic, an individual with a distinctive role to play. Ancient authors credited him and...

.

Some alternative English translations aim at greater literalness in their rendition of Ephesians 3:21: Young's Literal Translation

Young's Literal Translation

Young's Literal Translation is a translation of the Bible into English, published in 1862. The translation was made by Robert Young, compiler of Young's Analytical Concordance to the Bible and Concise Critical Comments on the New Testament. Young produced a "Revised Version" of the translation in...

 and the Darby Translation have "of the age of the ages", Webster's Revision

Webster's Revision

Noah Webster's 1833 limited revision of the King James Bible focused mainly on replacing archaic words and making simple grammatical changes. For example: "why" instead of "wherefore", "its" instead of "his" when referring to nonliving things, "male child" instead of "manchild", etc. He also...

 has "throughout all ages" while the New Living Translation

New Living Translation

The New Living Translation is a translation of the Bible into modern English. Originally starting out as an effort to revise The Living Bible, the project evolved into a new English translation from Hebrew and Greek texts...

 has "through endless ages". In many modern English-language translations of eastern orthodox texts,
such as the Divine Liturgy of St. John Chrysostom

Divine Liturgy of St. John Chrysostom

The Divine Liturgy of Saint John Chrysostom is the most celebrated Divine Liturgy in the Byzantine Rite. It is named after the anaphora with the same name which is its core part and it is attributed to Saint John Chrysostom, Archbishop of Constantinople in the 5th century.It reflects the work of...

 the phrase is often translated as 'unto ages of ages' .

The phrase occurs twelve times in the Book of Revelation

Book of Revelation

The Book of Revelation is the final book of the New Testament. The title came into usage from the first word of the book in Koine Greek: apokalupsis, meaning "unveiling" or "revelation"...

 alone, and another seven times in epistles, but not in the gospels:

• Galatians
  Epistle to the Galatians
  The Epistle of Paul to the Galatians, often shortened to Galatians, is the ninth book of the New Testament. It is a letter from Paul of Tarsus to a number of Early Christian communities in the Roman province of Galatia in central Anatolia...
  
   1:5,
• Ephesians 3:21,
• Philippians 4:20,
• 1 Timothy 1:17,
• 2 Timothy 4:18,
• Hebrews
  Epistle to the Hebrews
  The Epistle to the Hebrews is one of the books in the New Testament. Its author is not known.The primary purpose of the Letter to the Hebrews is to exhort Christians to persevere in the face of persecution. The central thought of the entire Epistle is the doctrine of the Person of Christ and his...
  
   13:21,
• 1 Peter 4:11,
• Revelation
  Book of Revelation
  The Book of Revelation is the final book of the New Testament. The title came into usage from the first word of the book in Koine Greek: apokalupsis, meaning "unveiling" or "revelation"...
  
   1:18, 4:9, 10, 5:13, 7:12, 10:6, 11:15, 14:11, 15:7, 19:3, 20:10, 22:5.

It is taken up in medieval Christian liturgy

Christian liturgy

A liturgy is a set form of ceremony or pattern of worship. Christian liturgy is a pattern for worship used by a Christian congregation or denomination on a regular basis....

, such as in the by Thomas Aquinas

Thomas Aquinas

Thomas Aquinas, O.P. , also Thomas of Aquin or Aquino, was an Italian Dominican priest of the Catholic Church, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus, Doctor Communis, or Doctor Universalis...

, in Veni Creator Spiritus

Veni Creator Spiritus

Veni Creator Spiritus is a hymn believed to have been written by Rabanus Maurus in the 9th century. It is normally sung in Gregorian Chant and often associated with the Roman Catholic Church, where it is performed during the liturgical celebration of the feast of Pentecost...

, Gloria Patri and numerous other instances. When it is followed by an Amen

Amen

The word amen is a declaration of affirmation found in the Hebrew Bible and New Testament. Its use in Judaism dates back to its earliest texts. It has been generally adopted in Christian worship as a concluding word for prayers and hymns. In Islam, it is the standard ending to Dua and the...

, the last two words (saeculorum, Amen) may be abbreviated Euouae

Euouae

Euouae is a mnemonic which was used in medieval music to denote the sequence of tones in the "seculorum Amen" passage of the lesser doxology, Gloria Patri, which ends with the phrase In saecula saeculorum, Amen...

 in medieval musical notation.

It does not occur in the Old Testament

Old Testament

The Old Testament, of which Christians hold different views, is a Christian term for the religious writings of ancient Israel held sacred and inspired by Christians which overlaps with the 24-book canon of the Masoretic Text of Judaism...

, which has other expressions for eternity, in Latin "for eternity and beyond", rendering the Hebrew , LXX , in English Bible translations usually also given as "for ever and ever".