A phrase commonly used to describe the cold weather outside as cold weather outside causes a male's testicles to become a lot tighter and move closer to the body. A phrase usually used when it is colder than usual this phrase describes the way a mans/boys testicles bollocks
will shrivel up and become very small when cold. Every time it is cold this happens to a boy which is one of the reasons why they always have their hands down their pants. The testicles are shrivelled, tighter, harder and very cold and only warm heat will make them dangle again. The testicles correspond with the penis as the penis also shrinks and becomes a lot smaller when it is freezing or when a boy is outside in cold weather shrinkage
. Basically when a boy is outside in cold weather his whole genitals are very small as a boys whole genitals shrink when they are cold but the term 'bitter bollocks' specifically relates to the testicles shrinking.
It is bitter bollocks today.