Verb - kukaza - I guess that it is causative from kaa. The translation is : 1 fasten, tighten, make tighter, close, compress
2 emphasize, highlight, give emphasis to
Passive form from kukaza is kukazwa - be emphasized
My guess is that it's a fairly old causative form of -kaa, meaning "to make stay" and the meaning has changed over time to mean "to fasten", "affix", "make firm".
There is another causative form from -kaa, which is -kalisha, meaning "to settle (someone/something)", "to seat (someone/something)".