Hey interestingly, just surfed the net
Not all male sikhs are singhs, and female sikhs are kaurs!
Apparently Singh means Lions and Kaur means Prince
and some ancient Sikh king gave the name Kaur to his
daughters
(because he wished they are 'equal' to his sons)
so it became sort of like a customs
but apparently lots of Sikhs also have both kaurs and singhs in
their names
regardless of male or female
this is cool. something new i learnt today 
***Oops apparently only ONE website says this, most still
says its generic 'title' Singh to males, and kaur to
females
But the history of it is interesting...apparently a long time ago,
the surnames used to reflect the caste system. when they abolished
it, they made all men and women have similar surnames.
Wiki says "The tenth Sikh guru, Guru Gobind Singh, made it
mandatory for Sikh females to use the second-name Kaur and for Sikh
males to use the second-name Singh.[1][2] The Guru said, "You are
my beloved princess, my daughters. You must be respected. How can
this world be without you?".
Kaur provides Sikh women with equal respect to men. The Guru Gobind
Singh said, "You dont have to take anybody else's name. You are an
individual, you are a princess, and you keep Kaur as your last
name.
