Moses,Elias and John the Forerunner, Christ and the 40 day fast ... these are 'precursors' if you will. And Christ said, "when you fast..." indicating a continuance. The Didache records that fasting was a practice in the early Church.
The particular fast before Pascha developed during an era (iirc) when there were an increased number of conversions. Incoming catechumens would fast for a period before baptism and communion. Within communities, members would join the fast and increase their prayer for the catechumens. Presently, Great Friday is a 'time' for renewal of our baptismal vows.
Fasting from particular foods, etc (including what comes out of the mouth
) Like the earlier fasts mentioned in the Bible, fasting is a dedication to God, a time of increased prayer and self-inspection, and preparation to "ascend the mountain" - the resurrection of Christ and the benefit that His sacrifice and victory offered to all.
There is also the 'winter Lent' (in preparation for the Nativity), the Apostles Fast, the Dormition Fast, the weekly Fasts (Wed., Fri.) and scattered Fast days before or during particular Feast Days and commemorations (ex., the Beheading of John the Baptist). In total, they number roughly half the year.