Why is the Great Fast called Quadragesima, ‘the forty days?’

The Great Fast of Lent continues forty days, besides the week of Christ’s Passion (Great and Holy Week), which is reckoned separately.

After the example of the Lord Jesus Christ himself, who fasted forty days in the wilderness (Mat 4:2; see Q486), as Moses (Exo 34:28; see Q492) and Elijah (1Kg 19:8; see Q542) had fasted forty days before him.