In oaths and asseverations, esp. at the reverence of God. archaic and rare after 17th cent.

Used to express affirmation, assent, or agreement: yes. Sometimes reduplicated (cf. sense A. 1c). Cf. och aye at och, int. 2. Now archaic and regional…

In the conclusive expression, that's flat (a) formerly = that's the absolute, undeniable truth; (b) a defiant expression of one's final resolve…

or my name is not ——: expressing asseveration. Also if (…), my name is not ——.

my eye (also rarely †my eyes): an expression of surprise, disbelief, or denial; (occasionally as n.) nonsense. In recent use also (dismissively) with…

I'm a Dutchman, i.e. some one that I am not at all: as the alternative or consequent clause to an assertion or questioned hypothesis. colloquial.