In the '50s knitting patterns in the UK for men's knitted attire would always have adverts/pictures of the most ammazing/good looking men. This therefore became a term to describe how good a man looked on the Atractive Scale - Knitting pattern is close to the top. (Knitting pattern guy is a phrase often used too)
An inevitable patch of hairless scrotum where the testicles mostly rest against the gusset of the gentleman's underwear, resulting in friction baldness.
After a few years of carefree post-pubescent abandon, eventually every guy will suffer from male pattern balls.
To fix yourself/get yourself together after doing some stupid ass shit or just picking up yo damn life. Also, means to get yourself into line/know your place.