I am writing a story about a man who doesn't know his past, or his name. I have to reveal his name later in the story. Until then, how do I refer to him or narrate his dialogues? My story is in third-person view.
Are you a gamer? Because such a thing happens a lot in games haha.
Take the Fallout Series for example, all characters have voice lines but the player can choose his or her character name and it's way to costly(and just plain impossible) to record dialogue for every possible name the player can choose.
So in the first game everybody just refers to him as "The Vault Dweller" because he came from a Vault. In Fallout 2 the player character is referred to as "The Chosen One" The third "The Lone Wanderer" and in the Spin-off "The Courier" after his profession.
And in the most recent game, Fallout 4, the character is called "The Sole Survivor" because he/she is the only survivor of his/her people. Such a name could be used for your character, something that would only fit him (best case something that happened to him/her just before the story starts/how he lost his/her memory) But seeing it is rather weird to just call somebody the "The Sole Survivor" the other characters can talk about him/her in a describing way. Best to do this is to clearly state his appearance, especially that what makes him/her stand out. If it's the only character who has red hair " red" would be a typical nickname to have when nobody knows his/her real name. Or distinctive tattoo (of a snake) on his arm could be the basis of his new nickname.