See also https://enlinko.com/. The calculations here are snappy.

I do not know which one was created first.

"Relatedness" here is according to ... something ... Approximately but not exactly the likelyhood that words appear near to one another in a large corpus of text. Probably doing lookups on something crunched by google books.

Thanks for posting about Enlinko. I'm author of it, i've published it 24 days ago:

https://news.ycombinator.com/item?id=35630451

Domain for this game has been created 9 days ago. So, i think someone was heavily inspired by my idea.

I understand that anyone can make game with same idea, but i'm bit sad that Enlinko haven't got such traction on HN as this game.

As for relatedness, my game uses semantic vectors from this model https://github.com/commonsense/conceptnet-numberbatch