There is some confusion over the words backpack and bagpack. What is the difference between a backpack and a bagpack? A backpack is a type of bag, usually with two straps that go over the shoulders, that is used for carrying items. The word backpack comes from the fact that this type of bag normally rests on the back of the person wearing it.
A bagpack, on the other hand, is not a real word. It is simply a mispronunciation of a backpack. So, if you want to be correct, stick with backpack.
The term backpack is the proper word to use when referring to this type of bag. However, you may hear people say bagpack instead of backpack. While this is technically incorrect, it has become somewhat accepted in society. So, if you do hear someone say bagpack, you can be pretty sure they are referring to a backpack.
The term backpack comes from the early 1900s. It is based on the word knapsack, which was used to describe a bag that was worn on the back. The word backpack first appeared in print in 1897.
The term bagpack is a recent invention, likely created due to the mispronunciation of backpack. This incorrect version of the word has become somewhat accepted in society, likely due to the fact that it is so similar to the correct term.
If you want to be absolutely correct, stick with backpack. But if you are just looking to be understood, either word will probably work just fine.