Why is the number 2 spelled “two”? Find out in this TED-Ed about spelling: “Making sense of spelling – Gina Cooke”
Her use of an onion as a metaphor is unusual, don’t you think? But paying attention to etymology is part of language noticing. I think it makes language learning more interesting and it also often makes words easier to remember. Learning Japanese, I pay special attention to the radicals. In English, paying attention to the roots of words, prefixes and suffixes is a similar strategy.
If you (used to?) think that English spelling and pronunciation was hard, try Welsh:
He’s pronouncing this town’s name: Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch and you can learn to pronounce it, too.