Cellar Door

There's a short scene near the end of Donnie Darko (2001) wherein the main character, a troubled teenager (Jake Gyllenhaal), is talking to his recently-fired English teacher (Drew Barrymore), and written on the chalk board behind her are the words "Cellar Door."

What's cellar door? Donnie asks.

She replies: This famous linguist once said that of all the phrases in the English language, of all the endless combinations of words in all of history, that Cellar Door is the most beautiful.

There are questions about the origin of this idea, but it's interesting to consider. This comes from a 1955 essay by Tolkien:

"Most English-speaking people…will admit that cellar door is 'beautiful', especially if dissociated from its sense (and from its spelling). More beautiful than, say, sky, and far more beautiful than beautiful. Well then, in Welsh for me cellar doors are extraordinarily frequent, and moving to the higher dimension, the words in which there is pleasure in the contemplation of the association of form and sense are abundant."

I favor "mason jar." Also "Little Pee Dee."