М209
HE МОГУ ЗНАТЬ
obs, now
humor (sent
Invarfixed WO (a respectful negative reply) I cannot answer because I do not know the answer
that I wouldn't know (, sir)
I wouldn't (don't) know, sir(in limited contexts) that I daren't judge (, sir).
Formerly used in the military as the negative reply of a subordinate to an officer of higher rank.