When I first happened upon 毋乃, I first guessed its meaning as "not this". Then I consulted p 1007, ABC Chinese–English Comprehensive Dictionary (2003). I can't access the "slightly revised through July 2005" ed.
2wúnǎi 毋乃 F.E. <wr.> Is it not ... ?
So why was my first guess wrong? Why doesn't 毋乃 mean "not this"?
How does 毋乃 compound to mean "Is it not ... ?"