Warning the following questions might seem silly

I was wondering if anyone knows what the letters all over Doom's armor mean, do they have some meaning or are just made up signs from Valve?

Also the 3 pendants with eyes on them, what do they mean if they have some meaning?

Hope you can clear this for me since I'm a huge lore geek and I don't believe that some designs are just random nonsense

Can't wait to read your thoughts on the matter!