Differences between "frank" and "honest"?

Question

I found a lot of people say "Frankly" or "To be frank" while the others say "Honestly" or "To be honest". I know both of them mean that sb. is going to say sth. which is true in a direct manner. But, I keep thinking that if there is a difference between them and if yes what is it? I am informed that in English as well as in many languages, some words are pretty same in meaning with each other, one of them is preferred by some people just because they like it. Like teenagers like to say some words which they think can make them cool. The case of "frank" and "honest", is it like this?

Answer 1

They are slightly different. To be frank is to be direct, whereas to be honest is to tell the truth. However, if I start a sentence with "frankly" vs. "honestly" the meaning is very close; either way I'm going to be direct about an uncomfortable truth.