http://www.ldoceonline.com/dictionary/sake_1 See Definition#2.
Not a teacher.
Student or Learner
What does "for goodness sake" mean?
It's a euphemism to avoid saying God's name in vain.
And note that there should be an apostrophe after "goodness". It's "for goodness' sake".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.