One of another name of Lord Shiva is  Neelkantha (Blue Throat) legend is that Once all the Gods and the demons met there to consult how to become immortal. So they decided that they would hunt for Amrit (the celestial ambrosia) the giver of immortality, so they decided to churn the ocean to extract Amrit,the churning yielded various assets like kamadhenu (divine cow) and the kalpavriksha (divine tree),goddess Lakshmi and many precious things also from the depths of the ocean,but in the  first of all , what emerged was the most vicious poison Halahal, that poison was incredibly dangereous so that  the fumes of that poison choked the three worlds and all the living creatures started to die.Nobody was able to stop or bear that poison then Shiva came to the rescue.As there was no any place to throw the poison Lord Shiva dranked that and without swallowing it held the poison in his throat.His throat turned blue and since then Lord Shiva is also called Neelkantha or the one with a blue throat.