honest John

God's honest truth

Unquestionable, absolute truth.

Honest Abe

A forthright and honest person.

if I'm honest

to be honest

John Hancock

A person's signature.

John Henry

One's signature.

John Q. Public

A generic individual; some hypothetical average or ordinary citizen.

make an honest woman

To marry (a woman), especially if there is an existing sexual relationship.

Master John Goodfellow

The penis.