Heading into work this morning, I read an excerpt from Rose George’s new book Nine Pints: A Journey Through the Mysterious, Miraculous World of Blood on the Guardian. This particular section of the book documented the author’s visit to the “UK’s only leech production business.” Personally, I had no idea there was still a market for medicinal leeches in the UK, but by the sounds of it business is pretty good.

The excerpt on its own was interesting enough, but what really got me thinking was the mention of the Latin names for medicinal leeches - Hirudo verbana and Hirudo medicinalis. Assuming (rightly) that hirudo means ‘leech’ in Latin, I immediately thought this could well be the origin of the Japanese word for leech hiru.

Japanese had considerable contact with German during the Meiji Era, and this has noticeably influenced the terms used in medical contexts. I reasoned that the Latinate term for ‘leech’ might have been introduced along with other Western medical terms at this time and then made its way into more general use, presumably displacing whatever native term had been used earlier.

But when I started looking for evidence to confirm my theory, I couldn’t find anything. Zilch. Nada.

Although hiru is normally written in kana (ヒル), something one would expect from a loanword, it also has its own kanji (蛭). With a couple of notable exceptions¹, European loanwords are written almost exclusively in katakana. Hardly a convincing start.

Moreover, none of the European languages from which hirudo, or something like it, could have come has a similar word for ‘leech.’ Here’s the word for ‘leech’ in the relevant European languages.

• German - Blutsauger (lit. ‘bloodsucker’)
• Dutch - bloedzuiger
• English - leech
• Portuguese - sanguessuga

Even the Romance language here doesn’t use the Latin term. Nothing in the above is remotely related to hirudo.

Lastly, and most importantly, none of the Japanese dictionaries I consulted considered hiru a loanword. Plausible² though it was, my theory was built on a strange, and strangely compelling, coincidence. Lesson learned, I guess.

Actually, the more I learn about loanwords in Japanese, the less I trust my intuitions. It’s a topic that first seems satisfyingly simple, but ends up being satisfying precisely because it isn’t.