Greetings, Bob.

Here's some information about the meaning of the word "yanga" that is found in this verse of the song "Wheel, Oh, Matilda" (that you posted above on December 23, 2011 from Noel Dexter, Godfrey Taylor, "Mango Time: Folk Songs of Jamaica". Musical score on p 122.)

Matilda walk an' yanga so-so,
Matilda walk an' yanga so-so,
Matilda walk an' yanga-so-so,
Tun di waata-wheel, O Matilda.

-snip-

The word "nyanga" or "yanga" is found in a number of African languages. Yanga is used as names for provinces, rivers, mountains, in Gabon, Congo, and South Africa. "Yanga African Sport Club" is the name of the club which has won more Tanzanian Premier League titles since 1968 up to now and "Yanga" is the name for panpipe orchestra music in Mozambique. Also, Gaspar Yanga—often simply Yanga or Nyanga—was a leader of a slave rebellion in Mexico during the early period of Spanish colonial rule. [see Wikipedia]

However, I think that the Jamaican word "yanga" had its source in the Nigerian pidgin word "nyanga". The "yanga" form of that word is still used in Nigerian pidgin today. Two "contemporary" examples are Fela Kuti's record "Trouble Sleep Yanga Wake Am" and a Nigerian Hip-Hop tune by a group called Outrageous entitled "Yanga".

The meaning of "yanga" in that Wheel Oh Matilda song is best given by two entries in the Dictionary of Jamaican Slang:

From http://books.google.com/books?id=_lmFzFgsTZYC&pg=PA484&lpg=PA484&dq=walk+and+yanga&source=bl&ots=N7IvqnTzr8&sig=7Q3Rz0m7ygyjrxdeg1cBvTTQOPM&hl=en&sa=X&ei=Nx_-Tt_XIsny0gGl8fDoDA&ved=0CD4Q6AEwBTgK#v=onepage&q=walk%20and%20yanga&f=false

F. G. Cassidy: Dictionary of Jamaican English Second Edition (University of West Indies Press ; 1980 ; originally published by Cambridge University Press in 1967; page 484)

Yanga – probable related to nyanga; dance about in joy; yangalala- be happy; perhaps influenced by American spelling yanga uncontrolled, carelessly done; To move (in dancing and walking) in a shaking or swaying way that is "styling" and "provocative"

1925 Beckwith 81 "Man da yawn. Man da yanga!", –"Yonga is a dance in which the body is shaken in all directions; 1943 GL Clar. "Yanga, walk, and stumble." Han "Yanga" swaying walk of women; Kgn "Yanga" a stylish way of stepping by women characterized by swinging of the arms and swaying of the head; 1950 Pioneer 41 "See yah de music sweet yuh se'! All de fowl dem start fe yanga an merange roun de room."; 1955 FGC "Man/yangga way of walking, step quite cute.

Yanga – a dance; see quotes
1925 Beckwith 81 –"Yonga is a dance in which the body is shaken in all directions"; 1963 T. Murry UWI, Yanga is a fast dance rhythm. The dancer has hands on hips and pushes pelvis and knees forward and back."

-snip-

Based on those entries and also based on the information cited in Martha Warren Beckwith and Helen Heffron Roberts' book "Folk-games of Jamaica",* p. 64, at Google Books, I would say that "yanga" in "Natilda walk an' yanga so-so" means "switch" (as in "walk provacatively"; "strut" this way (like so) [the player shows how she can walk in a sexy manner].

* "Wheel, Oh, Matilda" is a singing game song and not a dance folk song. From that Beckwith and Robert's book

"The players dance about in the ring and sing while one player looks for a bangle thrown on the ground within the circle. When she finds it she catches it up on a stick while all the others sing the second stanza."


-snip-

Also, here's more information about the word "yanga" from the fieldwork of Kenneth M Bilby among Jamaican Maroons in 1977-1978

http://memory.loc.gov/service/afc/eadxmlafc/eadpdfafc/2002/af002001.pdf

Kenneth M. Bilby Jamaica Maroon Collection
AFC 1983/008
(American Folklore Center)
Prepared by Michelle Forner
March 2002

"The audio and video recordings include examples of various "pleasure" (yanga) and "business" (nyaba) styles of dance and music.". p. 4

-snip-

This information points to the possibility that the word "yanga" (and maybe also the game song and later folk song "Wheel, Oh, Matilda") came from the Jamaican Maroons. Be that as it may, I definitely believe that "yanga" is another Jamaican word that has its source in Nigerian pidgin.