Is thiS supposed to be some Loony Tunes joke? ACME is the name of the protocol.
The Let's Encrypt community also made some fun references to the Roadrunner cartoons in the early days.
(1) The reference implementation of the ACME server was originally going to be called Anvil, but was renamed to Boulder. (A later lightweight testing implementation is called Pebble.)
(2) A later ACME client was called "dehydrated", after, well, take a look: https://github.com/dehydrated-io/dehydrated
(3) I'm pretty sure I'm forgetting another roadrunner joke here somewhere