[Not-so-subtly he also stretches with his foot to kind of kick his bedsheets at her? Stop freezing, oh my god.]

It might not be a not-Earth thing. But Morse was something that was created centuries ago, like in the 1800s. It's basically a way of translating texts into audible or visual cues. Like lights, or pulses or clicks. A lot of tech uses it too to transmit messages over a long distance. There's a whole alphabet and everything.

This--[A gesture to the letter.]--is something someone wanted to minimize and get through.