Wikipedia
The Manikongo or Mwene Kongo was the title of the rulers of the Kingdom of Kongo, a kingdom that existed from the fourteenth to the nineteenth centuries and consisted of land in present-day Angola and the Democratic Republic of Congo. The Manikongo's seat of power was M'banza-Kongo, (also São Salvador in 1570–1975) the present-day capital of Zaire Province in Angola, from where he would appoint governors for the provinces in the Kingdom and receive tribute from neighbouring subjects.
The term "Manikongo" is a Portuguese alteration of the KiKongo term Mwene Kongo (literally "lord of Kongo"). The term wene, from which mwene derived is also used to mean kingdom, and is attested with this meaning in the Kongo catechism of 1624 with reference to the Kingdom of Heaven. The term "Mwene" is created by adding the personal prefix (Class 1) Mu- to this stem, to mean "a person who performs the functions of the kingdom".
Mani is a spelling deformation of this original term, which is attested in very early texts, notably the letters of King Afonso I of Kongo, where he writes, in his letters to the Kings Manuel I and João III of Portugal in 1514 concerning the "moinepango" (mwene Mpangu, a provincial authority), in which the orthography reflects its actual pronunciation. Mani was not only used to mean "king" it was also applied to anyone holding authority, so provincial and sub-provincial officials also were called "mani". In spite of the spelling problem, virtually all writers, both Kikongo speaking and Portuguese, including the kings of Kongo themselves, used the term in regular correspondence.