Bip39 cdn https://www.tumblr.com/generalllamacolor/787594721599078400/can-you-depend-on-online-bip39-generators-a Though it utilizes BIP32 technique you are able to nonetheless import BIP39 seeds into Electrum wallet. Also other than BIp32 there is BIP44 Variation which some wallet use for your generation of seeds. For words that have only 3 letters, there isn't a 4th letter. One example https://sociallawy.com/story10711883/bip39-wordlist-english-github-bip39-ian-coleman-for-dummies-https-t-me-bip39-chat