What does he mean by "bless my soul"?

Question

FULL EXTRACT

"In my conscience--truly--I protest," honestly bewildered, "bless my soul, sir, I don't know you--really, really.

Answer 1

its is a quotation that i use often , i think its is biblical, literally to have ones soul, blessed, used in this context it is a gentle supprise?

Answer 2

its another word for suprise or disbelief

Answer 3

Make his soul pure, so that he may know him.

Answer 4

As God is my judge, he who can see into my soul can tell I'm telling the truth.

Answer 5

(God) bless me (or my soul) an exclamation of surprise, pleasure, indignation, etc.

any help? I think mainly it's indignation, because he was doubted.