Why do people in NY say tushie?

( I recently traveled with my son to visit family. Hubster was at home. I soaked up the quality time and the gold my little bug dropped left and right. I had nearly forgotten this one and just discovered my note.)

After one week with my NY family reunited in NY, my son asked, “Mama? Why do people in NY say tushie?”

It’s a funny thing to notice but he’s right on. I, although raised with tushie ( tushy?), tend to say bootie. Let’s bring tushie back to Calfornia!