Fever stick?

What on earth is a fever stick??? I cannot guess what it is, if it is not a thermometer and I do not think that a thermometer has any resemblance to a stick!

First, a stick is much longer than a thermometer. Second, a stick is something you can rely on, which is not physically possible with a thermometer.

Further, you cannot say that a dear child has many names, because I do not think there are many who like to have taken the temperature in the butt... or even to have a stick up in the butt for that matter...

The reason for the use of the word "fever stick" can, of course be that he or she cannot remember that it's called a thermometer... but where is the association to "stick"?