The fruit of apple trees is a popular food in many countries . Some word experts say that no other fruit is used in more English language expressions than the apple . For example , you can be the apple of someone's eye , meaning the most loved . You can upset the apple cart , meaning to create disorder . If your apple didn't fall far from the tree , you are very much like your mom or dad . And if you are compare apples and oranges you are comparing two things that are so different that any comparison is really not productive . And today , we have yet another apple term . To explain it , we need to go back to school . In the United States , people have long used the apple as a sign or symbol for education . Teachers and school officials often use apples in announcements and on posters hung in classrooms and school hallways . Candidates for school board positions often put an apple on election campaign materials . And many makers of school supplies put images of apples on their products . But why is the apple a symbol of education ? Some historians say this tradition began in the 1800s when settlers were moving to what is now the western United States . Back then , the U.S . government did not provide money for schools in the western frontier . The early settlers were responsible for making the schoolhouses and operating them . They also had to provide housing and food for the teachers . Students would bring teachers food from family farms . This would often include potatoes , vegetables and apples . Apples were a fairly common form of payment since they grew easily in many different climates . And they were used to make apple cider , a popular drink . Over the years , the tradition of giving food , in this case apples , as payment changed . It became a way of welcoming a teacher on the first day of class and hopefully leaving a good impression . Americans looked at apples as not only sweet and tasty , but really healthy . They are also colorful , more so than potatoes . So , they make a better gift . So that is how apples became popular gifts for teachers . And giving apples to teachers became a way of trying to curry favor with them . To curry someone's favor means you try to win them over by giving them something . You know , if you often give your teacher an apple , he or she may look kindly on you when they grade your next test . And if that apple is a beautiful , shiny one … well , your chances of getting better treatment is increased . And that is where the term apple-polisher comes in . Not only does an apple-polisher bring in an apple to get better treatment from the teacher , they also keep it nice and shiny . This makes sure it will be the most beautiful apple on the teacher's desk ! The singers Bing Crosby and Connie Boswell sang about this in the 1930s song , “Apple for the Teacher .” We use this as a noun and a verb . When you apple-polish , you use gifts or say nice things to improve your situation . We have other words that mean the same thing . We also call this type of person a kiss-up , toady or boot-licker . Another popular one is teacher's pet . It is an apple-polisher's dream to become the teacher's pet – much to the anger of fellow classmates .