Bendera comes from Portuguese bandeira, and is also quite close to Spanish bandera. Those three words are related to English band ("strip of material"), and also more distantly with bond, bind and bend.
Why is it not "ya tanzania"?
taifa is a ma-class noun, so in the singular it takes the la genitive particle https://en.wiktionary.org/wiki/taifa#Swahili
"The Tanzania flag is beautiful," should have been accepted. 19032020
Agree. I put this and it was rejected. Reported