Athams is abbreviated "-mas", which represents "christmas without the christ".
Guy2- I celebrated Athmas.
Guy1- What's that, like atheist christmas?
Guy2- Sorta, but not really. I ate athmas burritos, decorated my athmas tree, and gave an athmas present to my cat.
Guy1- That sounds awesome! I think I'll celebrate athmas next year, since Jesus never actually existed.