By what other name was the disciple Thomas called?

Answer: Didymus

John repeatedly refers to "Thomas called Didymus," one of the Twelve.

“Then Thomas called Didymus said to his fellow disciples, “Let us also go, so that we may die with Him.” Now Thomas called Didymus, one of the Twelve, was not with the disciples when Jesus came.”— John 11:16, 20:24 (BSB)