Chakra is the concept in Hinduism and Buddhism that there are various focal points in your body where energy is concentrated. The word comes from Sanskrit cakra, which meant "wheel", because it was implied that chakra was a "wheel of dharma" or "wheel of time" in various sources. Through Proto-Indo-Iranian, cakra further derives from the Proto-Indo-European root keklos, which could mean "wheel" or "circle". Keklos also became the Ancient Greek word kyklos, which became Latin cyclus, which became cycle; and the Proto-Germanic word hwewlaz, which became Old English hweol, which became Modern English wheel. It's pretty crazy that those words, which all seem so different, are connected by only several millenia of change, which isn't that much on a larger time scale of things.

Zarathustra was an ancient Persian religious leader who started Zoroastrianism. He's immortalized today through Friedrich Nietsche's book Also Sprach Zarathustra and the musical piece named after it. There are several etymological proposals for his name, but the most widely accepted one is that it comes from a combination of the words zarant, meaning "old", and ushtra, meaning "camel" (implying that Zarathustra owned old camels, not that he was one). Zarant comes from the same source as the Greek root gerontos: the Proto-Indo-European reconstruction gere, which meant "to grow old". Ushtra also has Indo-European cognates that imply a PIE origin, but there there are no reconstructions for it. It probably had the same meaning for a while and a generally similar sound, though.

In recent days, there's been a lot of misinformation on the Internet about the etymology of the Japanese word for "thank you", arigato. Some claim that it comes from the Portuguese word obrigado, which also means "thanks". On the surface, it looks like it may be possible, since there are a ton of Portuguese words in Japanese due to contact with early traders (which I discussed yesterday). However, that etymology is too perfect to be true. It shifted over time from the word arigataku, which meant the same thing and was used more than a hundred years prior to the Portuguese arriving. The roots there are ari, which meant "to exist" and katashi, which meant "difficult". The combined definition of "difficult to exist" later shifted to "rare", which became "special", which became "nice to have", which became "thank you". That's a lot of semantic change, and even cooler than an Indo-European origin.

In 1550, the kingdom of Portugal monopolized trading rights with Japan, and that basically lasted up to the Dutch entering the region in the seventeenth century. Relations were still really close until the Tokugawa shogunate isolated Japan in the 1630s, and, as such, a lot of Portuguese words were borrowed into Japanese (especially because of new ideas and technologies being brought over by missionaries). Here are some of the most interesting borrowings:

• The Portuguese word for "cup", copo, became kappu in Japanese
• The Portuguese word for "button", botao, became botan in Japanese
• The Japanese name for deep-fried seafood and vegetables, tempura, comes from a Portuguese word meaning "seasoning", tempero
• The Portuguese word for "bread", pao, became pan in Japanese
• The Portuguese word for "tobacco", tabaco, became tobako in Japanese

And much more! There's a rather engrossing Wikipedia glossary on this that you should check out if this fascinating topic further interest you.

The noun filet first emerged in the early fourteenth century. For a while, there were a bunch of accepted spellings, including felet, fyllet, filett, and fillit, but around the time when the word was verbified at the start of the seventeenth century the most common forms were narrowed down to fillet and filet​. It comes from the Middle French word filet, which had the rather interesting definition of "ribbon". The connection there is that early styles of the dish were prepared by being tied with a string. Further back, we can trace it to Latin filum, which meant "thread", and that traces to a Proto-Indo-European word sounding like gwhi and with the same meaning. This makes fillet related tot he words file and profile, but those are stories for another time.