Okay so basically, you have to think of a word that is completely irrelevant to the last one, in every way. It must not associate to the last word in any way at all.
So for example:
"Turtle"
then
"Cat"
Would be bad because they are both animals, like
"Medieval"
and
"Modern"
Would be bad, coz they are both eras of time.
Understand? Well, if not, then don't play

But if you do, here's your first word:
Seventeen