The creator of Jenga!, Leslie Scott, grew up speaking Swahili in East Africa. When he created the game he did not want to call it an English name, so he named it Jenga, derived from the Swahili word for build.
Nope. Lavatory should be accepted; report it and the error will be fixed. As a general guideline, double check Duolingo's dictionary with another dictionary like Wiktionary if you aren't sure. Occasionally the sentence is right but the dictionary is wrong.