@Tᴚoɯɐuo I'm really not sure that interpretation is the only possibility.

In any case, nothing in the context of the original sentence clarifies what or how much was consumed in a particular "fourth helping". It only mentions "fourth helpings at every meal". To call that a "name" is a ridiculous leap in logic since there is no parallel in common use in English. "Second helpings" when used (Which is far more common than 4th) functions as a standard noun phrase -- not a name

@eques So you see no nuanced difference between "a fourth helping at every meal" and "fourth helpings at every meal"? There's nothing going on here that is at all reminiscent of "second breakfast" or "elevenses" in The Fellowship of the Ring?

@Tᴚoɯɐuo I'm saying "fourth helpings at every meal" is not precise AND that the context doesn't specify any details about what these helpings consisted of; i.e. whether it's a fourth serving of a single item or a fourth plate. It only specifies that at every meal Molly compelled him to consume 4 helpings.

@Tᴚoɯɐuo There is nothing special about "second breakfast" in phrasing, but note a) it's a singular noun outright (you don't find "Bilbo and the dwarfs had second breakfasts"). and b) the ordinal serves to distinguish it from the breakfast preceding it which other peoples are familiar with

Elevenses is in origination, yes a plural. No, there is nothing reminiscent of it nor "second breakfast" in the line "forced him to eat fourth helpings". I never even considered such a parsing until you proposed it.

@eques "second breakfast" is the name for that meal in the canonical sequence of hobbit meals. That's what is "special" about it. There's no article there. It's not "a second breakfast".

@Tᴚoɯɐuo It being a name says nothing about "fourth helpings" being a name. In fact note that it is singular in form "second breakfast" not "second breakfasts"

@Tᴚoɯɐuo Could you give us a sentence in which fourth helpings takes a singular verb? For example, Fourth helpings was had just sounds wrong to my ears (I'm not a native speaker of English, however).

Okay, thank you.