Doctor Who: 14 Cool Details In Steven Moffat & David Tennant's Silence In The Library Commentary
6. Why Moffat Chose The Name "Vashta Nerada"
When naming the various creatures, characters and locations in their stories, a lot of writers will try and get really clever by giving these made-up-monikers some sort of hidden meaning.
We've seen this in Doctor Who lots of times before - probably the most famous example is that the letters in "Doctor Who" can be rearranged to spell out "Torchwood" - but sometimes, names are just... names.
Case in point: the Vashta Nerada. During the commentary, Moffat is asked where the idea for that name came from, and - even though you might assume that there's some sort of nifty secret behind it - he states that "it's completely made up", and that he actually went out of his way to check that it didn't have a deeper meaning.
Hilariously, he also adds that he thought Tennant would "sound cool" saying it (he's not wrong!), which is mainly what made him settle on this particular name.