This blog post traces it to a songbook called "Choral Folk Songs from South Africa" compiled by Pete Seeger and Robert DeCormier (and cites this thread): https://songidblog.com/2019/11/utawena-1961-kingston-trio.html

Apparently the correct title is "Ut'he Wena." Some notes from the songbook here: https://www.wisemusicclassical.com/work/45537/

Video of a choir singing what I assume is the Seeger/DeCormier arrangement, slightly different from the Kingston Trio's: https://www.youtube.com/watch?v=xS0pFs87nqQ