• 01.083 and very quickly he was plain Mr. Baggins of Bag-End,
• 12.008 from Bag-End long ago.
• 12.068 was to be brought back all the way to Bag-End Under-Hill.
• 19.036 of Bag-End, Underhill, Hobbiton.

It’s the name of something, therefore JRRT can call it anything he likes… yet since it bears a hyphen, we shall put it under scrutiny.  OED says there’s no such word, hyphenated or not.  As we know, it’s the proper English pronunciation of cul-de-sac.

UPDATE: 2021.10.21  Yes, indeed, it is hyphenated thusly in The Annotated Hobbit revised and expanded edition annotated by Douglas A. Anderson.  Someone implored me to be very certain indeed.  In fact, I can’t find it unhyphenated in the work at all.  But the caution is well-merited!  According to Richard Blackwelder, Bag End is never hyphenated in The Lord of the Rings.