Very interesting because its the first time i read something that let me suspect that they study a bit deeper western african (and more precisely the Mandingo culture)
Bala (or Balan, related to the limit of phonetic translation) is the correct name of the instrument in root language (called Julakan, Mandikakan, Malinkekan or Bamanankan, depending the country or the related ethnia but virtually the same spoken language)
Balafon means in fact "the sound of the Balan"
Balanfola litteraly means"The man who's making the sound of the Balan"
And Unlike other instrument in negro-african culture, the Guinea Balan is heptatonic (as diatonic scales) and much easier to adapt to chromatic intervals
AFAIK, "balani" seems to be a contraction of "Baladeni" (the small Balan)