Shirsh means head and shishya means one who has no head. There is a story about Guru Gobind Singh, who was the last guru of the Sikhs. He had many followers, but he wanted to define what real discipleship was.
Once he called his followers and they came in thousands. He said, "I want people from among you whom I can sacrifice to fulfil a purpose." Of course everybody said, "Forget it, I am not going to be sacrificed."
One person said, "Ok, guru is asking, so I am willing." He raised his hand. The guru called him inside a tent, took out the sword, and outside people heard a big noise, whack! The guru came out with the bloodstained sword. He said, "One more." Now everybody's heart was palpitating, wondering what was happening inside. However, somebody was brave enough and said, "Ok, I will sacrifice my life." The guru said, "Come inside the tent," and another, whack! Again the guru came out with the bloodstained sword. Like this, he called four people for only four were willing in that crowd of maybe ten thousand. After the four had gone in and were killed, the guru came out of the tent with the bloodstained sword, and said, "Who is next?" Everybody ran away, thinking, "Who is going to be killed by this crazy guru?"
What they did not know was that nobody was killed. Inside the tent only a goat was killed for dinner. All four shishyas were alive and well.
Guru Gobind brought these four people out, and said, "These are my four disciples on whom I entrust my work."
—18 March 2012, Paduka Darshan, Munger