Bar Hebraeus Says that Mark was the First (and Only) to Call his Work a 'Gospel'

The beginning of the Gospel of Yeshua the Messiah. (Mark 1:1)

Note: that baptism is the beginning of the Gospel according to the arrangement of Mark, we know this: that before our Lord was baptized, he did not preach nor announced [something]. But after baptism, and be tempted, he began to say: repent, the kingdom of heaven is approaching. And St. Basil said that Mark used this term first, the Gospel, and we know this [fact] for this: the other three evangelists did not use it. [Bar Hebraeus Commentary]