POP TARTS

Now I have a question thats been on my mind for a few weeks now and i've decided to Blogg about is. Why DO they call a POP TART a POP TART????? I understand the POP part. You can POP them in the toster or POP them in the microwave. The part i dont understand is the TART part. I never had a TART POP TART. I mean all my POP TARTS have been sweet. So shouldnt they call them POP SWEETS.