What do you think of teaching children the correct terms for male/female body parts?

My cousin and I both had a spirited debate with two of our aunts. My cousin has taught her preschoolers to use the words "penis" and "vagina" which I am also planning on teaching to my daughter. Our aunts feel this is highly inappropriate and children should be taught words like "wiggy" or "hoo-hoo". I was just wondering how other people felt about this.