The Greek prefix krypto-, Latinized to crypto-, means “hidden” or “concealed.” The science of codes and ciphers is called cryptography. For the longest time the only people who ever talked about “crypto” were computer scientists and mathematicians who worked with sensitive data. They came up with all kinds of schemes for hiding (encrypting) and then revealing (decrypting) that information. Our entire economy now depends on the robustness and practicality of these cryptographic tools. Every time you log on to the internet you rely on cryptographic technologies to protect your identity and your transactions.
But these days when people say “crypto” they mean that crypto-currency nonsense. It seems like all of a sudden everyone is an expert on “blockchains” (an interesting technology that emerged from cryptographic applications), much like everyone was suddenly an expert on viral epidemiology when COVID hit!
Krypton wasn’t isolated until 1898. It’s a so-called noble gas meaning it is mostly inert and does not react with other elements. It was hard to separate krypton from the others of its kind (helium, neon, argon, xenon) and thus it seems appropriately named.
Superman comes from the planet Krypton. And we all know he is vulnerable to kryptonite. I always had to spend time in science class explaining that Superman is make-believe and that there’s no such stuff as kryptonite. Comic books present a more appealing reality, I suppose. The periodic table is pretty dull by comparison!
Krypton is used in lasers and for fluorescent lighting. It is a fission product of uranium decay and can thus indicate the presence of nuclear fuels. People could tell that North Korea and Pakistan were able to process those materials by detecting krypton in the air. You might find krypton (or argon) in the gap in your double-paned windows. Over time that stuff leaks out and the insulating properties are compromised. Krypton causes narcosis if breathed in and could have potential as an anesthetic. Our atmosphere contains only 1 ppm of krypton compared to about 5 ppm for helium, 18 ppm for neon, and over 9300 ppm for argon.