In many English literature the phrase-part "to tell you the truth" shows up. But in contrast to the literal meaning, this doesn't mean the characters were first lying about this.
In Dutch these are the following meanings for the Dutch counterpart ("Om de waarheid te zeggen,..."/"De waarheid is dat...")
- The person was first lying; and
- The truth is quite inconvenient (thus some kind of warning that you won't like the following part of the sentence).
In some English literature however, characters simply make statements that aren't at all inconvenient (or they weren't lying in the first place).
What is thus the semantical meaning of "To tell you the truth,".