In a book I've read some characters are answering questions with "Why, ", e.g.
Why not come to me? you ask, and I must answer, Why, because I did not trust you, my lord.
and they never mean it seriously, always with some insolence. However, the amount of insolence and how rude it really sounds I cannot grasp.
Can I use such a construction in an informal speech without any offence meant? In a not-so-formal letter to a boss, for example?