Ask 10 high school students what is the “sin” function. If you are lucky some will recite a formula: opposite/hypotenuse.
Now ask what the result means: for instance if you say the sin(30) = 0.5, what does it mean? In other words, what 0.5 represents?
Well, if you someone tells it a percentage of the circle radius, you are indeed a lucky person.
This site — search for the words Try it — has a beautiful animation to demonstrate how it works. Note that when the angle is 30, the sine is 0.5, what represents 50% of the radius length. Simple, isn’t it?
SINE comes from the Latin SINUS, meaning a bend or gulf, or the bosom of a garment. Also, it has anatomical meaning: the cavities or bays in the facial bones.
But wait! In Italian, sine is seno that also means breast. In Portuguese, sine is seno, but breast is seio and bell is sino. All of then have to with the sine format, that resembles either a breast or a bell.
Tip: another great source to understand Maths instead of knowing formulas by heart is this one: https://betterexplained.com/