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Over a couple of centuries, the long vowels of English (vowel sounds held for longer than their short partners) moved, and the letters that spelled them mostly stayed put. For the most part the spelling didn't change to follow the sounds, so English spelling that looks wrong is often a record of older speech.

Print the word BLUE in red ink, ask someone to name the ink, and watch the answer stall. The word and the colour are both shouting, and the word is louder.

One grain of sand is not a heap, and one more grain never seems to make the difference. Follow that thought all the way and you end up somewhere absurd.

In Jane Austen's Emma, a young man nearly confesses something, and the narrator tells us he "was more in love with her than Emma had supposed". It reads like a fact. It isn't. It's Emma's own guess, slipped into the narrator's voice without a single quotation mark, and once you can spot the trick, you'll find it all over the novels you read.

Medieval English speakers tied on "a napron". Say that out loud a few times and you'll hear the problem: it sounds almost exactly like "an apron". Over the generations the n slid across the gap between the words, and the same slip, running the other way, turned "an ekename" into "a nickname".

Dub the sound of one syllable onto a film of a mouth shaping another, and people report hearing a syllable that's on neither track. The trick is old, simple and stubborn, and it shows sight reaching into hearing.