そういう訳で、診察所の方の人達と口を利くのはあたしだけといってよい位だったわ。そりゃああたしがお侠{きゃん}だからだけれども、先生の小間使いですもの、そりゃどうしたって診察所との交渉が多いわよ。ええ、こりゃ漢語よ。
甲賀 三郎 著 『ニッケルの文鎮』 青空文庫 No.1428
I could not understand the actual meaning of 「ええ、こりゃ漢語よ。」
According to some dictionaries, 漢語 just refers to a word originated in China / a Chinese word. It would not fit this context...
The whole passage of your quote can be translated as:
For that reason, it was almost only me who was able to speak to the people of the clinic. Though I admit I look a bit pert, I’m only a messenger girl of my master, and naturally have to deal with the doctors and staff of the clinic. It requires a bit of understanding of (medical) gibberish.
漢語 literally means Chinese language, but in a colloquial usage it means "difficult, technical words," because 漢文 was read and understood only by intellectual people in Meiji and Taisho era, not to mention earlier than those time.
In 永井荷風’s famous "墨東奇談” published in 1947, much later than this work, the heroine, Otsuru, a prostitute, whom the hero, Taneda, a school teacher describes as a beautiful crane among a bevy of chickens - 鶏群の一鶴 - tells him that her father was “an intellectual man who used to read “四角な文字” (square letters),” which means 漢字. You’ll understand that 漢字 looks square and Kana looks round in its shape.
There is also a Japanese word, チンプンカンプン meaning totally incomprehensible or nonsensical, which came from 珍文漢文 (ridiculous writing in Chinese language).
In net, 漢語 here means “gibberish” or Greek to laymen.
