"Drive a caucus in out my head."

The story:

My eight-year-old sister were singing along to this
song in the car with my parents. She knew all the
words and was really belting it out when we heard
her practically screaming "drive a caucus in out my
head." My mom stopped the music and said, "What did
you say?" She repeated the lyric and my mom said,
"Whoa, that doesn't even make sense!" My sister
realized that it didn't, and, being eight years
old, started repeating it nonstop for around
fifteen minutes.