*(s)ter-

The core idea of this root was:

stiff, rigid

Pretty simple, but it evolved into quite a few different directions.

Here’s an (incomplete) list of English family members:

• stark – (“strong, rigid”, shifted toward serious)
• starch – (“makes mush thick, stiff”)
• stern – (“rigid”)
• to start – (“jumping up quickly, stiff muscles”)
• to startle – (Same as “start” but shifted toward the cause)
• to stare – (“stiff gaze”, same as German “starren”)
• starve – (“stiff corpse”, same as German “sterben” – to die)
• torpedo – (“make numb”, from a Latin name for an electric ray fish that numbs you. Military name first used for sea mines, because they “sting” your ship)
• stereo – (Greek word for “solid”, they used it among other things for “solid 3D perception, I suppose)

The root is also the origin of the Slavic word star-, which means old.