Youse guys missed the point.

The thingy is the pendulum.

The only reason that it looks like something else is that you can't see the whole thing in most traditional metronomes.

All of the names you've suggested are names for something it looks like but that it isn't.

If you're going to produce a latinized nomenclature it must include all of:

"The part of the compound penudulum that looks like an upward extended swingy thingy."

The request was also for a name for the adjustable weight, which, if it must have it's own name must include all of:

The adjustable weight on the upper extension of the compound pendulum that can be moved to adjust the moment of inertia of the swingy part for the purpose of changing the frequency.

Now quit foolin' around and get accurate.

I will reserve judgement on whether the stated principle of taxonomic naming, that "it doesn't have to be based on real Latin or Greek as long as it sounds like Latin or Greek" will be acceptable. They only allowed that because they estimate that there are 300 million species still requiring names, and you've only got one tiny part to handle.

John