That raises another question, did the title “Son of Man” refer to an apocalyptic figure before Daniel was written? I don’t think so, but I’m not positive.

In the apocalyptic sense the term originates with Daniel, though it’s wrong to refer to it as a title here. Daniel simply says that a figure in human form or human appearance came on the clouds of heaven - in immediate contrast to the four beasts. Both the beasts and the human figure are symbols for nations or peoples: the beasts are oppressive empires, the human figure represents the saints of the Most High who remain loyal to the covenant.

The phrase ‘Son of man’ does occur prior to Daniel, however. One of the most interesting usages is in Ezekiel, where the prophet is addressed repeatedly as ‘Son of man’ and instructed to proclaim judgment and restoration to Jerusalem, which seems highly pertinent to Jesus’ usage, though less overtly so than Daniel 7 (see The Coming of the Son of Man, 51-52).