- As far as I know, there was never a dictionary that pairs idioms and only idioms from different languages. It's true that numerous dictionaries of idioms for a specific language have been published. The explanations or definitions of the idioms may be in the same language as the idioms, or in a different language. When they are in a different language (called target language for the sake of argument), more often than not a matching idiom in the target language cannot be found, and a wordy explanation is provided. The Multilingual Idioms List project handles this situation differently: leaving the entry blank on the target language side. This is actually a good thing. It either positively acknowledges such lack, or catches readers' attention and waits for other native speakers to find a good idiom in later times.
- The List is multilingual, not limited to two languages. Unlike any published dictionary of idioms where the source and target languages differ, the contributors, or in a sense lexicographers, of the crowdsourcing List are not language professionals. This is not a big problem since the List is not a highly technical dictionary. The big advantage, on the other hand, is that the contributors are almost all native speakers. This is significant because good or even correct usage of idioms is very much dependent on real life experience in the language environment. Being native may be more relevant to this project than being professional if being both is not possible.
Today, I made a small contribution to the List, by adding the column Chinese (since no one before me had done that), and providing a dozen or so idioms, as follows:
|a bitter pill||不得不吞的苦果|
|a piece of cake||小菜一碟|
|add insults to injury||雪上加霜；往伤口上撒盐|
|an arm and a leg||倾家荡产|
|beat around the bush||拐弯抹角|
|best of both worlds||两全其美|
|bite the bullet||硬着头皮上|
|burn the midnight oil||开夜车|
|cast in stone||板上定钉|
|from A to Z||从头到尾|
|have eyes in the back of one's head||眼观四路，耳听八方|
|hit the road||上路|
|let the cat out of the bag||抖包袱|
|kick the bucket||见阎王|
|off the hook||如释重负|
In Chinese, there are different types of idioms. 成语 (literally probably "solidified or invariable phrases") are more formal and literary, mostly of four characters, such as "自相矛盾" ("self-contradictory"), "纸上谈兵" ("talk of military strategy (only) on paper"). 歇后语 (literally "sentences said after taking a rest") are colloquial proverbs, such as "和尚打伞，无法无天" ("A monk holds up an umbrella. No hair|law. No sky.", or "The dharma is obscured and heaven blocked."). Obviously some idioms are in neither category, and yet are expressions that cannot be literally interpreted, such as "硬着头皮上", literally "go ahead with hardened scalp", which I consider matching "bite the bullet" in English.
I can think of one improvement that may be made on the current List. It would be nice to provide a place to enter the literal translation of an idiom and optionally a brief explanation. For instance, I would love to add that the Chinese idiom "软肋" for "Achilles' heel" literally means "soft rib" because the rib bone is relatively weak and fragile, and that "雪上加霜" for "add insults to injury" literally means "add frost on top of snow", a phrase that may not need an explanation. With these additions, the List would be more fun to read. So for instance, we'll know that instead of "beat around the bush", the Chinese "make turns and scratch corners" ("拐弯抹角"), and the French "turn around the pot" ("tourner autour du pot") instead. While English-speaking people consider Greek a difficult language ("It's all Greek to me!"), the Chinese language is regarded by by far the most other peoples; "Chinese" occurs 24 times out of about 100, compared to 12 for "Greek", on the Wikipedia page for Greek to me. Through this List, we know a little more about different cultures. But technical limitation for the List is understandable; it is in the format of a spreadsheet, where adding two more columns (literal meaning and explanation) for each language would make the list too hard to read. Other options include adding comments to the spreadsheet cell, where the comments are not shown unless the mouse is over the cell.Overall, this is a great project. I hope they'll set up a Wikipedia page, with versions in many different languages contributed by the same volunteers that build the List.