Oonsoo is is a solitaire/patience game involving Hanafuda cards. The objective is to sort each of the twelve suits in order, such that each foundation has a single suit/season. As you play, you can deal an additional row of cards until all cards are eventually in play. In this regard, it is somewhat similar to Spider solitaire. If unfamiliar with Hanafuda cards, the game also has a handy reference screen.
Oonsoo was written by Bradford W. Mott with Seunghee Lee in 1994. Per the announcement file, it is supported on Linux 2.x.x, Ultrix 4.3, HP-UX 9.0 and Solaris. There was, at one point, a web site for the game, which is now only available thanks to the Wayback Machine.
I am having difficulty finding any information about the original solitaire game: did it exist prior to its software implementation? The only web results I can find are of this exact game, PySolFC, and a mobile port. If there is a non-English name for it, I can't seem to find it from the English one. If anyone knows more, please fill me in!
The following is an unsuccessful session playing Oonsoo. The variant in XPat2 is easier.
Oonsoo is no longer in the Debian repositories, but can still be found in the Debian archive pool. It required some minor changes to compile, so I am including my patches for oonsoo. These are very minor, so it wasn't that much trouble to run it on modern Linux. Refer to README for build instructions.
That said, for most people, PySolFC is probably simpler, as it includes this style of solitaire as well.
More general information on old X games, including build tips can be found in the Old X Games article.
If the above video does not work for you, it is also available on my YouTube channel.