This song gained popularity for tourists to better learn the language of what ever country they were in. Its all over eastern Africa mainly Zanzibar, Kenya and Tanzania.

“At the time, Them Mushroom, the band, was playing covers of European hits to entertain the tourists vacationing on the Kenyan coastline. One night, while taking a break between two songs, he heard tourists trying to speak Swahili and practicing words like Jambo (“Hi”), Habari gani (“How are you?”), and Hakuna matata (“No problems”). That gave him the idea to write a song with simple phrases in Swahili, which would help visitors learn the language while dancing to the band’s music.” 

https://www.203challenges.com/a-brief-history-of-the-jambo-bwana-song/ 

Youtube Link: https://youtu.be/Kg8NeUl-aQQ