Long before brand referred to a company’s manufactured product, a brand was a mark seared with a branding iron (often into the flesh of a living being). Bran is the outer layer (husk) of cereal grain and the products made from it.
Both brand-new and bran-new (meaning “conspicuously new and unused” or “recently introduced”) have been in use for centuries. According to Merriam-Webster’s online dictionary, brand-new has been used as an adjective since about 1570. (The dictionary hyphenates both spellings, with bran-new considered a variant of brand-new.)
Some of us remember the song “Papa’s Got a Brand New Bag.” (James Brown was awarded a Grammy for Best Rhythm & Blues Recording of 1965). A Brand New Me was an album by Dusty Springfield that featured a song titled (or entitled, if you prefer) “Brand New Me”; it was released in 1970, the same year The Partridge Family released an album with a “Brand New Me” song. Other artists who have recorded songs and albums with “brand new me” in the title include John Michael Montgomery (2000) and Alicia Keys (2012).
By 1791, when the play Wild Oats by John O’Keeffe* was first performed, use of bran new was, well, not new.
Here it is again, in The Wonderful Wizard of Oz by L. Frank Baum**:
Though the first use of bran-new may have been a mistake, both spellings are now considered acceptable.
Even so, I think I’ll stick to brand-new.
* Available online through Project Gutenberg, http://www.gutenberg.org/ebooks/39060