The bible doesn't mention his mother's name, and this one sounds strange to me. It must be part of some legend, like
Anna is
Jesus' Grandmother according to Catholic tradition.
Google threw up this site, which at first sight seems to be reliable:
http://members.shaw.ca/jegure/sauldavidsolomon.htm
It says what I thought: that the two names are in fact one. They sound pretty much alike anyway. I assume NAZBAT is misspelt and should be NATZBAT with a Tsadik as a second consonant, so the verbal root in both cases would be N-TZ-B (Nun-Tsadik-Bet). Even more so as I can't find a verbal root N-Z-B.
The verb "natzav" means "to stand, take a stand" or "to be put". If this applies here, the name could mean something similar to
Seth, which is translated: "God has put (another child instead)" (of one that died). (Salomo originally means something quite similar, the peace-thing was later - sorry
Mike!)
But there seems to be another meaning of the verb "natzav" and this is in
Zach 11,16: "sound, healthy". The participle found here is "nitzavah", but "nitzevet" would just be an alternative form of this.
Hope this didn't cause even more confusion.
Andy ;—)