How to interpret「～そうになるのを、」

Question

I am having a hard time understanding the grammar of the following sentence.

贅肉がはみ出して落っこちそうになるのを、体に巻きつけてあるみたいな感じだ。

In isolation, the two parts make sense.

贅肉がはみ出して落っこちそうになる
[Her] excess fat stuck out, as if it were about to fall off.

...を体に巻きつけてあるみたいな感じだ
It was as though ... was wound around [her] body

But when combined with this のを、I cannot understand. の appears to nominalize なる, but this is part of そうになる which I am stumped with.

How should i interpret this? Thank you :^)

Edit: I've added the whole text, to provide better context. This is a description of Matilda's mother. Perhaps my incessant questions about Matilda will help someone else reading this book in the future :)

大柄な女で、髪はプラチナブロンド（薄い銀白色）に染めている。ただ、生えぎわのあたりにだけ、ネズミ色がかった茶色の髪が見えかくれしている。こってりとお化粧をしているが、気の毒なくらいにぶくぶくだ。**贅肉がはみ出して落っこちそうになるのを、体に巻きつけてあるみたいな感じだ。

Answer 1

For the form of the relative clause, see internally-headed relative clauses.

V～そう, as you probably know, means 'looks like [it will] V', 雨が降りそうだ, etc. This form is a な-adjective, and thus all the conversions that apply to those can be made:

問題になりそうなもの

and as in the example sentence, it can be turned into an adverbial phrase, with なる adding the sense of 'coming near to [looking like it will V]', e.g.,

焼け落ちそうになる, 'come near to burning down'.

Your translation 'as if about to fall off' quite captures the sense. なる seems not to offer much extra in terms of sense, so that there is only a subtle difference between

落っこちそうになるのを

and

落っこちそうなのを

Answer 2

贅肉がはみ出して

"[Her] excess fat stuck out and"

落っこちそうになる

more literally, "became like seeming to fall off"

Your translation seems fine to me, and putting those two ideas leads to the translation you offer for the first part in isolation.

〇〇になる is practically a set idiom (see for example the song title 風になる), but its individual parts still work normally. The basic sense of なる is "to become"; it's intransitive, and the に-marked part describes the state that the subject achieves.

の appears to nominalize なる, but this is part of そうになる which I am stumped with.

This そう on the other hand is a suffix for 落っこち, not part of the idiom. 落っこちそう (= 落っこちる + 〜そう) is the に-marked part of なる here.

Individual verbs are not nominalized; entire clauses (which, in the limiting case, contain just a verb) are. This part is fuzzy for me, but generally it seems safe to say that normally, what gets relativized is an implicit topic - which usually matches the subject.

The te-form み出して connects to the other verb なる, so they have the same subject, 贅肉, and implicitly the same topic, and that is what gets relativized by の. Thus:

贅肉がはみ出して落っこちそうになる

"[Her] excess fat stuck out, as if it were about to fall off"

【贅肉がはみ出して落っこちそうになる】の

"[Her] excess fat, which stuck out - as if it were about to fall off"

And that is exactly what fits in the ... of the second part.