Faithful but liar

We talked about his friend. He said, 'well, he's monoganous'.

I said, 'you mean, monogamous'?

He insisted, 'monoganous'!

So I got up from our breakfast table and fetched the Oxford Dictionary. I showed him the word that says, m.o.n.o.g.a.m.o.u.s. I said triumphantly, 'see? monogamous!'

He replied, with all the sincerity he could muster: 'That's what I said!'