“Thomas” means “twin.” The name was used to designate the author of a sayings collection used by Judean/proto-Christian congregations.
The meaning that first comes to mind is “identical twin.” But that meaning does not add any value: why attribute sayings to an identical twin? I suggest instead that “Thomas” was a fraternal twin. I propose that “Thomas” was a polite term that designated “synagogue adherent of Gentile origin.” The wisdom of the God-fearers was used in the synagogue by politely designating its collective author as the fraternal twin of the Judeans.
Now we can understand why there were multiple versions of the Gospel of Thomas in the Christian world. The text could be endlessly added to. That’s why we find material from the synoptic gospels (or similar to and therefore “authorized by” the synoptic gospels) in some versions of GThomas.
I note that GThomas was particularly popular in Syria. That is where it was ascribed to “Didymus Judas Thomas.” That is, “Greek twin–Judean–Aramaic twin.” I suggest that the expanded name was a political compromise to acknowledge the collection’s sources in these three traditions.
We can see the value to orthodox editors of including the name “Thomas” as one of the Twelve disciples in the canonical gospels. The name is an acknowledgment of and welcome to God-fearers.