Ruzuzu you have been hiding under your pretty cloak of two letter words for too long now. There are words of three and more words in the forest. Scuffle the leaves and they will flit, skittering away, farting vowels with their tails in the air.
A nickname based (generally) on "Aijā žūžū lāča bērni," which is my favorite Latvian lullaby. However, a cursory Google search for "ruzuzu" does yield the following reference: Coosemans M, Wery M, Storme B, Hendrix L, Mfisi B. Épidémiologie du paludisme dans la plaine de la Ruzuzu, Burundi (Epidemiology of malaria in the plain of Ruzizi, Burundi) Ann Soc BelgMed Trop. 1984;64:135–158. (Found on http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1116524/.)