Meaning of verbal suffix ～てくたっとしてしまう

Question

I've come across several cases of verbs with the suffix ～てくたっとしてしまう, but am unsure how to break this suffix down, or what it means exactly. It seems that this is the て-form of the base verb, followed by something that looks like くたっ, perhaps followed by the particle と and the verb する in the て-form, followed by the auxiliary verb しまう, but I'm having no luck finding a grammatical description of the middle part here (くたっとする?).

A quick Google search finds many examples of sentences using this kind of structure, such as:

• きんぴらごぼうなども、そのまま鍋に入れておくと、余熱で火が通ってくたっとしてしまうので同じような処理をする。
• レザーのクラッチバックというと重くてくたっとしてしまうイメージでしたが、これは全く違う印象でした。
• 冬はさむくてくたっとしてしまうので、暖かいお部屋に入れてあげるか、いっそ球根（というかイモですね）で越冬させるか。

Would anyone be able to clarify the grammatical function at work here?

Answer 1

くたっ is a mimetic word meaning something like "floppy", "tired", "withered", etc. It's a variation of くたくた / ぐだぐだ. くたっとする means "to become withered", etc.

When you have seen an unfamiliar mimetic/onomatopoeic word in the form of ～っと, it's a good idea to repeat the mimetic/onomatopoeic part and look it up in a dictionary. (e.g., look up にょきにょき instead of にょきっと) See: How are the giongo/gitaigo double form and tto form related (きらきら vs. きらっと)

You have parsed the remaining part correctly. To clarify, ～てくたっとしてしまう is not a set "suffix" at all. It's just four words: ～て + くたっと + して + しまう, meaning something like "and (it) ends up becoming floppy".