"Letter" Natural Recordings by Native Speakers
A letter is a written message, often in the form of a handwritten or printed document, that is used to convey information, express thoughts, or provide instructions. It can also refer to a letter of the alphabet, one of the 26 characters used to form words in written language.
The adjective "lettered" means having letters, written, or marked with letters, especially for labeling, indicating, or distinguishing purposes. It can also imply a certain level of education or literacy, as in "lettered scholars" or "lettered individuals".
Letterman refers to David Letterman, an American television host, comedian, writer, and producer who is best known for hosting several late-night talk shows, including "Late Night with David Letterman" and "The Late Show with David Letterman". The term is often used colloquially to describe a witty and clever individual who has a dry sense of humor and is comfortable being himself in front of an audience.