I get that dumbbells are bells that don’t ring, except they look nothing whatsoever like bells. Also barbells, kettle bells…no resemblance to a bell.
How did they come to be called this?
Kettle bells do look like the bell you hang from a cow’s neck. (Cattle bell? 
)
I’ve always assumed that was the origin.
How about this kind of bell?
They do make a sort-of cowbell clink when you slide them onto the bar, or stack them in a pile.
I love Southern belles.
Wikipedia is on it: Dumbbell - Wikipedia
dumb bells are called that because they originally used church bells with the clappers removed, ergo voiceless or “dumb”.
Kettle bells are called that because they are shaped like a cauldron or kettle, and bar bells are called that because they have a long bar connecting them.
(ETA) Scooped by Manduck, I see