What is top of the morning?

"Top of the morning" is an informal, traditional Irish greeting that is often associated with how people believe the Irish greet each other, although it is not commonly used in modern Ireland. It is a more formal and historically stylized way of saying "good morning." The expression is often perceived as representing a cheerful beginning to the day. The typical response to "Top of the morning to you" is "And the rest of the day to yourself."

It's worth noting that this phrase has been popularized through literature, film, and media, often used by non-Irish people when trying to imitate or reference Irish culture. As a result, it carries a bit of a stereotypical or even cliched connotation in some contexts.