I remember it being something along the lines of "Roll over on your tummy" followed by "Lift (or scootch) your butt up" followed by my pants/underwear being pulled down. Similar for both Mom and nurses. Often, I would see them approach me while shaking the thermometer down and knew what to expect.
Usually my mother took my temperature rectally. I was always lying on my tummy for doing so. So, this was always clear. When she wanted to take my temperature she just said:"Should we measure your temperature. prepare yourself, I will fetch the thermometer." Somehow, I like that. While taking my temperature my mother was always very caring. The "we" in the sentence suggested that temperature taking is something we do together: I provide the butt an she inserts the thermometer.
My temperature was taken rectally until I was about 10-11 years old. They could say something like “I think we better have to take your temperature. Please go to your bed and pull down your underwear!” After a while my mother or father came with the old style mercury thermometer in glass and with the metal tip already lubed in. It was always inserted slowly and carefully. First I felt the metal tip and it felt really cold. Then I could feel the shoulder of the thermometer being inserted as well. It was somewhat uncomfortable at the beginning, but it didn't hurt and after a while it felt not that bad. Even if the insertion was done slowly, it was at the same time done really resolute. I knew the thermometer had to be inserted and there were no way to escape from it...
I can only remember the phrasing one time at the doctor’s office.Doctor: “mom, can you help me to lay David down so I can get his temperature”
With a professional domme: "Ok sweetie, I'm going to take your temperature, right here in your little hiney."