Some publications, such as Fred Majdalany's State of Emergency: The Full Story of Mau Mau, claim that it was an anagram of Uma Uma (which means "get out get out") and was a military codeword based on a secret language-game Kikuyu boys used to play at the time of their circumcision. Majdalany goes on to state that the British simply used the name as a label for the Kikuyu ethnic community without assigning any specific definition.
Days of futures past?
“Something of Value” by Robert Ruark
Read it while on convalescent leave 1969!
Still recall some of it!
A good read.