‘B’ is for Ball ‘n Chain.
According to Wikipedia, a ball and chain was a physical restraint device historically applied to prisoners, primarily in the British Empire and its former colonies, from the 17th century until as late as the mid-20th century. A type of shackle, the ball and chain is designed so that the weight of the iron ball at the end of the short chain restricts and limits the pace at which its wearer is able to move, making any attempt at escape much more difficult.
“Sittin’ down by my window,
Honey, lookin’ out at the rain
Lord, Lord, Lord, sittin’ down by my window,
Baby, lookin’ out at the rain.
Somethin’ came along, grabbed a hold of me,
And it felt just like a ball and chain.”
Big Mama Thornton, ”Ball ‘n Chain”
made famous by Big Brother and the Holding Company featuring Janis Joplin