In the early centuries when the Church was under persecution, the Eastern Church held a feast on 6th January called Epiphany to celebrate the manifestation of Christ to the world at His birth, through the Eastern-Bethlehem Star and at His Baptism and Transfiguration. Epiphany was followed by a 40 day fast since Christ fasted 40 days in the wilderness where the Holy Spirit led Him after His baptism in River Jordan and the Devil later tempted Him (Matt 4 and Luke 4).
(1) And Jesus being full of the Holy Spirit returned from the Jordan, and was led by the Spirit into the wilderness,
(2) Being forty days tempted of the devil. And in those days he did eat nothing: and when they were ended, he afterward hungered.
To follow after Christ’s experience, the Epiphany Feast which had Christ’s Baptism as part of its commemoration especially in Egyptian Church was followed by a 40 day fast in preparation for baptism of new converts called catechumens who were also given intense discipleship teachings and ministrations during the period.
During the same early centuries, the Western Church also observed another 21 day Great Weeks fast in preparation for Catechumens for Baptism during Pascha or Easter celebration of Christ’s Passover. These Catechumenate preparatory fasts were usually joined by the whole Church both in Eastern and Western Churches for rededication to a new walk with Christ, along with the new converts.
After the Ecumenical Council of Nicaea in 325 AD when all the Churches (Western Latin Churches, Eastern Greek Churches, Syrian Churches and Egyptian Churches) came out of persecution and able to hold concourse and harmonize their programmes universally in unity, the post-Epiphany 40 day fast was eventually moved forward into the 21 day pre-Pascha fast. These Fasts occurred in the Springtide season so Lent (Anglo-Saxon word for Spring or Springtide) was used to designate the fast.