Recently, I was informed that introverts look for depth of knowledge whereas extorverts are about breadth of knowledge. This positions horizontal breadth or width as orthogonal direction to the vertical depth so that I started to think that broadness and breadth are not only semantically but etymologically identical. How much am I right?
Both are from the Anglo-Saxon (AS) brad, broad.
Breadth: AS braedu, from brad
Broad: AS brad
My source: Webster's New Collegiate Dictionary
Further Information from Online Etymology Dictionary (http://www.etymonline.com/index.php?allowed_in_frame=0&search=breadth&searchmode=term)
broad: Old English brad "broad, flat, open, extended," from Proto-Germanic *braithaz (cognates: Old Frisian bred, Old Norse breiðr, Dutch breed, German breit, Gothic brouþs), which is of unknown origin. Not found outside Germanic languages. No clear distinction in sense from wide.
breadth: 1520s, alteration of brede "breadth," from Old English brædu "breadth, width, extent," from bræd; probably by analogy of long/length