Garden History, Vol. 24, No. 1, Summer 1996, titled "The Tortuous Tale of 'Bear's Breech' the Puzzling Name for Acanthus mollis." The article gives a very in depth theory that essentially says the name came from it's medieval name, "branca ursina." They hypothesized that the bracts look like bear's claws - hence "ursina" and that "branca" morphed into breech over time. Whatever the case, I think the name quite cute and the flower is lovely.
I also found out that it can be invasive in areas. Although mine has gotten bigger over the years, it doesn't spread too much. And I love that I don't have to water it - it even survived last year's drought. Apparently it is recommended for xeriscaping because of that quality. Another perk is that you can dry these for flower arrangements! I haven't tried it yet but will definitely post later if that works out.