Howdy
Howdy is an informal greeting, commonly thought to have originated as a shortened form of the greeting "How do you do?". It was first recorded as part of the South England dialect in 1680. Literature from that period includes the use of "How-do, how-do" and "How" as a greeting used by the Scottish when addressing Anglo settlers in greeting. The double form of the idiom is still found in parts of Texas as "Howdy, howdy". Without regard to etymological beginnings, the word is used as a greeting such as "Hello" and not, normally, as an enquiry. As a result, it's not followed by a question mark. Punctuating "Howdy" commonly follows these rules:
(i) If "Howdy" is used as a complete sentence, it's followed by an exclamation mark.
(ii) If "Howdy" is the first word in a sentence, it's followed by a comma.