普段わたしたちが使っているカタカナ言葉、日本語じゃないのは分かってるけど、じゃぁ何語？　っていうことありませんか？
We use so many Katakana words in our daily lives.
Japanese characters consist of three types, chinese origin ones, Hiragana and Katakana.
We often use Katakana characters for refering to words from foreign languages.
We know it's not Japanese, but we often encounter origin-unknown words.

カレーのルーの　ルー　って何語？　って今日ふと思い調べてみました。
I looked up on the Internet to find out what language "loo (spelled soundwise)" is from.
We use the word "loo" for meaning "sauce mix cube", by the way.

結局ルーはフランス語なんですね。
It turned out to be spelled "roux" in French, but it's been pronounced "loo" in Japanese.

そして英語では何ていうかというと、 sauce mix cube　というそうです。
So, it's called "sauce mix cube" in English, then. Case closed!