> and the name

Frank Denis also wrote libsodium, so guess it is a pun by him? Don't think there was any lib{chemical element} popularised before that, and there's a few now, but could be wrong.

The first version was a rewrite of libsodium, that was small and contained in a single C file. Also introduced xchacha20 for the first time. Then, the Gimli paper was published, and libhydrogen was rewritten to take advantage of it.

Smaller than libhydrogen, there's now charm: https://github.com/jedisct1/charm , also a pun. The plan was to eventually add bottom (platform abstraction layer), strange (asymmetric cryptography), and top (high-level APIs) to build a modular, component-based library.