Bip39 c++ https://zanevnex175.lowescouponn.com/practical-use-a-python-based-bip39-seed-generator-in-the-real-world While it utilizes BIP32 technique you could still import BIP39 seeds into Electrum wallet. Also besides BIp32 there is BIP44 version which some wallet use to the era of seeds. For words that have only three letters, there is not any 4th letter. One example is With https://bookmarkvids.com/story21533947/bip39-vs-the-smart-trick-of-bip39-word-list-github-that-no-one-is-discussing-https-linktr-ee-bip39