In his book the number 42 is the “answer to the meaning of life, the universe, and everything” - calculated by a very big computer over a very very long time:
“All right,” said Deep Thought. “The Answer to the Great Question…”
“Of Life, the Universe and Everything…” said Deep Thought.
“Is…” said Deep Thought, and paused.
“Forty-two,” said Deep Thought, with infinite majesty and calm.” Douglas Adams The Hitchhiker’s Guide to the Galaxy quoted from GoodReads
Software developers like to use 42 as magic number, that’s a number without any real significance, which you could replace by any other number. Of course the name arc42 wouldn’t sound half as cool if we had choosen another number…