I've been hooked ever since I found out as a small child that Inuits have hundreds of words for snow. In reality they don't actually have many more words for snow than us, they just create compound words to increase their vocabulary, but the idea that a language reflects the experience of the people who speak it has stayed with me.
Another word that, to me, is uniquely of that country, is the Russian word toska. It's described by Vladmir Nabokov thus: At its deepest and most painful, it is a sensation of great spiritual anguish, often without any specific cause. At less morbid levels it is a dull ache of the soul, a longing with nothing to long for, a sick pining, a vague restlessness, mental throes, yearning. In particular cases it may be the desire for somebody of something specific, nostalgia, love-sickness. At the lowest level it grades into ennui, boredom.
In England, we're just bored. In Russia, one has a dull ache of the soul.
In Indonesian there's a word, jayus, which means a joke which is so unfunny, it makes us laugh. This is presumably very useful for Indonesian parents of children under the age of seven and should definitely have an English equivalent.
When we were in Northern Thailand, we stayed in an Akha hilltribe village in the jungle. The guesthouse manager had been helping an anthropologist to create an Akha dictionary. It was fascinatingly full of words that have no proper equivalent in English, many of them jungle related.
Victoria Wallop is a confirmed Londoner, with a love of travelling to far-flung places. She writes, tweets and solders silver for a living. She's useful in a pub quiz and adept at pulling leeches off small people.