DaVonna is a name made up of various different "bits and pieces" - here's some suggestions. Click on the hyperlinks for details of any of these names.
1) It could be a variation of
Davina, influenced by African-American naming tradtions.
2) It could be a combination of
Yvonne with the popular African-American name prefix
Da- - similar to
Lavonne.
3) It could be a variation of
Devon, again influenced by African-American naming styles.