The phrase “Son of man” appears multiple times in the Old and New Testaments.
In the Old Testament, the Hebrew phrase אדם בן (ben adam) translates as “son of man” and is used for a person, any named or unnamed person.
In the Greek New Testament, the phrase “son of man” is υἱὸς τοῦ ἀνθρώπου (huios tou anthrōpou), but is always used in reference to Yeshua (Jesus), either by Yeshua himself in reference to himself or by others in reference to Yeshua.
If Yeshua spoke Hebrew, and he used the Hebrew phrase ben adam, then he was simply claiming to be “a person.” Even if Yeshua spoke Greek, which I highly doubt, he would have used the phrase huios tou anthrōpou, which is the Greek translation of the Hebrew ben adam, and is still simply claiming to be “a person.”
However, there is one place in the Old Testament where a different phrase is used for “son of man.”
“I saw in the night visions, and, behold, one like the Son of man came with the clouds of heaven, and came to the Ancient of days, and they brought him near before him.” (KJV, Daniel 7:13)
A portion of the Book of Daniel, including this verse, is written in Aramaic and the Aramaic for “son of man” is אנוש בר (bar enosh). Now, if Yeshua were speaking Hebrew all the time, but used the Aramaic phrase bar enosh instead of ben adam, in reference to himself, then his listeners would know that he was calling himself the bar enosh from Daniel 7:13, the one who “came with the clouds of heaven.”
This is one of the many reasons why I believe that Yeshua always spoke in Hebrew. If Yeshua was speaking in Greek and he used the phrase huios tou anthrōpou, he is just calling himself a man. If Yeshua was speaking in Aramaic and used the phrase bar enosh, he is still just calling himself a man, as in Aramaic bar enosh means nothing more than a “son of man.” But if he were speaking in Hebrew, his listeners would expect the phrase ben adam if he were simply referring to himself as a “man,” but if he changed to Aramaic for this one phrase, then he is definitely referencing Daniel 7:13, a well-known messianic prophecy in the first century.