The long pointy thing that they pee out of is called a penis and the the things you asked about are called testicles. Some people call them balls, and some people just make up their own name for them.
If your talking about the flap under the shoelaces, that's the tongue.
The curvy thing under your lungs is called the diaphragm. It plays a crucial role in respiration by contracting and flattening when you inhale, creating more space for the lungs to expand and draw in air. When you exhale, the diaphragm relaxes and moves back up, helping to push air out of the lungs.
That thing that goes under the suit is typically a dress shirt and an undershirt. The dress shirt is worn as the main shirt and the undershirt is worn underneath for added comfort and to absorb sweat.
The part under a bra is typically called the band or underband. It provides support and holds the bra in place around the ribcage.
If we are talking about lever action rifles?Then the tube under the barrel is the magazine tube.
The thing under their body is called a foot
the round things under your car which roll when the thing moves.
The tongue
condenser
right under the hood on the driver side right up against the frame itself usally accompanied by a black round thing called clutch box
Under the objective lens there is a stage to put the specimen ( the thing you want to look at ).
Under the glove box on the passenger side. Black round thing.
They are actually just called gazebos. Pergolas are very pretty, too, to get married under.
permafrost is were every thing is frozen solid and it is always under 32 Fahrenheit all year round out side
A corset.
An udder.
under the steering wheel you have to take the how thing apart and its a round thing p.s. its connected to the turn signal lever