How can I determine if someone owns the intellectual property rights to a word game?

I found a really cool word game that I would like to implement as a mobile app, though I don't if anyone owns the right to the concept. I know there are many games out there, such as Poker or Crossword puzzles, that are in the public domain and I'm hoping this is one of them. I've done a patent search on google and a trademark search on the USPTO site and haven't found anything. How can I determine if someone owns the rights to the word game that I'd like to implement as a mobile app?

Thanks so much for your knowledge!

Well, you stated that you have done a little bit of research...I would consider doing both a trademark and patent search at the governmental websites. In addition, I would try a lot of different combinations of searches to ensure all possible bases are covered. If you can't find anything related (close enough where they could make a claim against you), then I think it's fair game.

Perhaps you could search and find similar or related apps that exist already (through a Google search). If you do find something similar, you could then use that as a basis to search through the USPTO.

Try to trace the history of the game. If it's old enough, more than 100 years, it's very likely that it's in the public domain.