I started playing Dungeons and Dragons in high school more than 40 years ago, and always admired the way D&D could pull in material from all know mythologies and tap into the history of high fantasy literature, from the Lord of the Rings to the old Conan novels. While I don't expect every phrase from this rich (but strange) heritage to show up in every dictionary, one huge pet peeve of mine is that the word GEAS is not in the Scrabble dictionary or any dictionary used by any online games I play. Heck, you can always find ROCS and LICHES and ghosts and goblins in modern games. But never GEAS. GEAS comes from the Irish, through Scottish to English. A GEAS is an unwilling quest, which can also be conveyed as a taboo, or the curse that will be bestowed upon you for breaking a taboo. If you take on a quest of your own free will, that's one thing. But if a demigod gives you a GEAS to walk to the ends of the earth, you're in for a world of pain. Wikipedia has ...
A blog of word lore and word-based games.