Open sesame!

The tale of Ali Baba and the Forty Thieves is world famous, so it's no surprise that it's just as well known in Japan. What did surprise me, for some reason, is the translation of 'Open Sesame!'.
開けゴマ (ひらけごま)
Literally, 'Open! Sesame'. Perhaps because it's a magic word, it hadn't occurred to me that 'sesame' would be literally translated.

However, ごま lends itself to some other Japanese phrases that don't translate quite as literally.

へそのゴマ
Literally 'navel sesame', an interesting way of describing belly-button fluff. Perhaps I'm weird, but it doesn't remind me much of sesame.

ごま塩ノイズ 
Sesame and salt noise: black and white noise. A common condiment is ground black sesame with salt, and it does look quite like static noise on a television, albeit more static than static noise, which, ironically, isn't actually static. The katakana word ノイズ means specifically 'random noise' rather than loud sounds in general.

ごますり or ごまをする
Grinding sesame: idle flattery. The verb here is する 'to grind; to rub'. Not to be confused with する 'to do', it conjugates normally, so the polite form is すります, not します. The grinding is specifically with a mortar and pestle, and the ground sesame sticks to everything it comes into contact with. Therefore, and this is a stretch, it means trying to 'stick' to everybody, hence flatter. This has led to a gesture for flattery: rubbing one hand against the other as though grinding sesame.

ごまふ　(胡麻斑)
'sesame freckled' is used in the names of flora and fauna to mean black spotted or speckled. The spotted seal is 胡麻斑海豹 ごまふあざらし, the kanji meaning a sesame spotted sea leopard.

ごまかす 
To deceive. Actually, this may or may not be sesame related. When written in kanji, these days it's usually written as 誤魔化す misunderstand + magic + -ise (verb forming ending, as in socialise), but this is 'ateji', with kanji used only for their sounds. One theory is that it comes from 護摩 ごま, a Buddhist cedar stick burning ceremony, with a verb ending かす. The ashes from this would be sold, but often you'd be more likely to be getting burnt garden waste from the not-so-devout ash salesman. So 'are you cedar-sticking me?' came to mean 'deceive'. The other explanation does involve sesame. 護摩菓子 (ごまかし), is sesame flavoured sweets, in this case referring particularly to an Edo period (1603-1868) cake called 胡麻胴乱 (ごまどうらん). This was hollow inside, so looked considerably much more substantial than reality. Therefore, 'sesame-caking' was outright deception.

The more interesting etymologies have come from http://gogen-allguide.com/.

Fun fun fun

The kanji 楽, fun, easy, was originally written 樂 and is supposed to be derived from a pictograph of some bells hanging from a tree. It was borrowed for its sound for the modern meaning, and it appears in a few other kanji. See if you can guess what these characters mean.

• 薬　grass + fun
• 擽　hand + fun
• 轢　car + fun

薬　drugs, medicine
This is a fairly basic kanji, and it's easy to remember the meaning. The other two characters are quite rare.
薬　くすり　drugs, medicine

擽　to tickle
As far as I can tell, the 樂 part is only there as a phonetic guide, but the constituent parts fit the meaning so well I'm surprised this character isn't better known.
擽る　くすぐ・る　to tickle

轢　to run over
Car fun! Joy riding? Well, one of the words this kanji is used in is  轢死. Car fun death? In the world of kanji, the most fun you can have in your car is to run somebody over. How macabre.
轢く　ひ・く　to run over


As gruesome as kanji gets, nobody really thinks that running somebody over is a barrel of laughs. The kanji 楽 comes from a pictograph of a tree with a lot of chrysalises, which referred to the saw-tooth oak. The chrysalises survived as the 幺 in the old character, today simplified as four dashes. Later an acorn was added, and this now is the most prominent part 白.

Then the character was borrowed for its sound. This is a very common phenomenon in kanji; the original meaning is completely lost, as its used for a more common homonym. In this case, the word for 'pleasure' or 'comfort'. To get the meaning of saw-tooth oak, tree is added to the left side 櫟, to tell the reader 'this is the tree 樂, I'm not using it to mean "fun" here'.

轢 is using 楽 for its sound, as they had similar pronunciations in Chinese, and, by a convoluted word association: a tree with acorns　→　acorns　→　small objects → small stones, it had the meaning of crushing small stones as you drive over them.

Big numbers

Japanese has had the good fortune of inheriting the Chinese number system. The way of building higher numbers is so logical that a learner can pick it up very quickly, and it makes arithmetic much easier for children, because they are already well aware of the concepts of hundreds, tens and units by the time they start school.

Powers of ten, however, are not quite as logical. In fact, the usage of the higher powers are not universally agreed on in the kanji using world. There were 下数, using increments of 10; 中数 using increments of 10,000; and 上数 where each number name was the square of the previous. In Japan 中数 became standard in the 17 century, although apparently remnants of the different systems persist elsewhere.

From 1 to 10,000, each multiple of ten has its own name.
一 いち 1
十 じゅう 10
百 ひゃく 100
千 せん 1,000
万 まん 10,000

Then the numbers go up in multiples of 10,000.
億 おく 100,000,000 (10⁸ a hundred million)
兆 ちょう 1,000,000,000,000 (10¹² a trillion)
京 けい 10,000,000,000,000,000 (10¹⁶ ten quadrillion)

That's about the limit as far as useful numbers go, but they do go much higher!
Even from 兆 (portent, omen) and 京 (capital city) characters are being reused. There isn't always a clear explanation as to why a particular kanji was chosen, as they are most likely phonetic borrowings.

垓 がい　10²⁰ The character means boundary or limit.
禾予(as one Kanji) じょ　10²⁴ The character for this is so rare that it isn't even in the basic JIS character set. The original kanji was 秭, which means 'piling up'. When writing this, I found that I could paste the kanji in the editor, but it wouldn't display on the published post.
穣 じょう　10²⁸ Lush, abundant.
溝 こう　10³² A ditch or narrow waterway.
澗 かん　10³⁶ A mountain stream. Two water related kanji in a row. Is there a pattern coming up? Sadly, no.
正 せい　10⁴⁰ Usually means 'correct', but has a minor meaning of 'long' which could be why it is used.
載 さい　10⁴⁴ Load or carry. Nothing could possibly carry anything this big! It also means write down or print, so is more likely to have the meaning 'something so large it cannot be written'.
極 ごく　10⁴⁸ Limit, extreme. The absolute highest number ever! Hang on a minute....

After that, Buddhism was clearly a major influence.

恒河沙 ごうがしゃ 10⁵² 恒 is a kanji transcription of the Sanskrit name for the Ganges, 河 is river and 沙 means 'sand', so the whole thing is 'the number of grains of sand on the River Ganges'. Quite poetic, really.
阿僧祇 あそぎ 10⁵⁶ From the Sanskrit for 'more than can be counted'
那由他 なゆた 10⁶⁰ From the Sanskrit for 'an extremely high number'
不可思議 ふかしぎ 10⁶⁴ 不可 is 'impossible', 思議 is 'conjecture' or 'guess'. An unimaginably large number!
無量大数 むりょうたいすう 10⁶⁸ Originally two words, 無量 is 'unmeasurably huge' and 大数 is 'a big number'. So together they make an gigantastically meganormous number.

100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000

 Still quite a bit smaller than a googolplexian, and slightly less than the total number of atoms in the universe.