Wasn't actually a name being taught - the teacher showed the diagrams, identified deuterium and tritium by name, and then mentioned they were sure there was an isotope-specific name for H1, and as I was also sure I'd heard of it at some point I went and looked it up. I think I may have heard of it in reference to Hydrogen not actually having a correct place in the periodic table, it's not actually group 1? Kind of like it's the "zero-eth element".