The Kirpan (ceremonial dagger) has been part of the Sikh attire for over 300 years, since the creation of the Khalsa discipline.  The Khalsa order was established on March 30th 1699 by the tenth Guru of the Sikhs, Guru Gobind Singh Ji.  The name Khalsa means 'Pure'.  The Khalsa are Sikhs who have undergone the sacred ceremony of Amrit.  Upon initiation to the order of the Khalsa a Sikh must follow strictly the rules which are assigned by the order, one of the rule being the attire a Sikh wears.  Five items must be kept on a Sikh at all times these are detailed below:

1. Kesh – uncut hair to represent the natural appearance of sainthood. It is argued by some that the requirement is Keski instead, a small turban to be worn underneath a bigger turban. However the latter idea is not contradictory to the former, since the purpose of the Keski is to preserve the kesh.

2. Kanga – a small comb.

3. Kaccha – warrior short trousers, also denotes chastity.

4. Kara – steel bangle as a sign of restraint and bondage, and a symbol of dedication to the Guru. Guru Gobind Singh proclaimed that by wearing Kara all fears will be removed.

5. Kirpan – a sword for defense. The Kirpan is a symbol of dignity, power and courage. Kirpan is from Kirpa (act of kindness, Sanskrit) + Aan (self respect, Persian).

The Kirpan in no way signifies aggression or some kind of warlike attitude, its meaning is much deeper, it signifies the defense of those who are weak, for the protection of the Sikh people and to uphold what is right.  Its shows the power, dignity, and courage held within a Sikh a power that can only be worn by those who are devout to the order of the Khalsa and know when and why it can be used.  It is also a reminder to the bearer of there duty to defend the weak and those who are unable to defend themselves, not to cower away from there duty as a Khalsa.  The tenth Guru himself stated that the sword could only be lifted when all other means to negotiate had failed, the lifting of the sword is a last resort.  The Kirpan can only be used in self-defense and is in no way as an offensive weapon. 

"When all other means have failed,  it is then righteous to take the sword in hand."
Zafar-namah, Dasam Granth
Shri Guru Gobind Singh Ji - The Tenth Master