<P> The curvature of the female back is a frequent theme in paintings, because the sensibilities of many cultures permit the back to be shown nude - implying full nudity without actually displaying it . Indeed, the practice of showing explicitness on the lower back has been performed for centuries . Certain articles of clothing, such as the haltertop and the backless dress, are designed to expose the back in this manner . The lower back is typically exposed frequently by many types of shirts in woman's fashion, and even the more conservative shirts and blouses will reveal the lower back . This happens for a variety of reasons - the lower waist area is a pivot point for the body and lengthens and arches as a person sits or bends . Secondly, woman's fashion typically favors tops that are waist length, allowing the back to be left bare during slight movement, bending or sitting . The back also serves as the largest canvas for body art on the human body . Because of its size and the relative lack of hair, the back presents an ideal canvas on the human body for lower back tattoos, mostly among young women . Indeed, some individuals have tattoos that cover the entirety of the back . Others have smaller tattoos at significant locations, such as the shoulder blade or the bottom of the back . </P> <P> Many English idioms mention the back, usually highlighting it as an area of vulnerability; one must "watch one's back", or one may end up "with one's back up against the wall"; worse yet, someone may "stab one in the back", but hopefully a friend "has got one's back". The back is also a symbol of strength and hard work, with those seeking physical labor looking for "strong backs", and workers being implored to "put their back into it". </P> <P> Historically, flagellation of a person across the back with a whip was both a common form of punishment of criminals, and a common means of forcing slaves to work . As well, self - flagellation, as in self punishment, may include the use of whipping oneself . This is one method of mortification, the practice of inflicting physical suffering on oneself with the religious belief that it will serve as penance for one's own sins or those of others . While more moderate forms of mortification are widely practiced--particularly in the Catholic Church--self flagellation is not encouraged by mainstream religions or religious leaders . A well - known instrument used for flagellations is the infamous Cat' o Nine Tails, a nine - corded whip with one handle enabling a much more effective whipping than would be possible with only one lashing at a time . </P>

What is the back part of the head called