namba noun "a hammer" (NDAM), namba- vb. "to hammer" (NDAM). According to VT45:37, Tolkien may have considered the alternative form lamba, but the source is obscure and lamba is assigned a quite different meaning ("tongue") elsewhere.
Quenya
lamba
hammer
namba
hammer
lamba (2) noun ?"hammer" (possibly an alternative form of namba, q.v., but the source is obscure and namba is to be preferred) (VT45:37)