Bit is the unit usually used for describing entropy, information density, and channel capacity, regardless of whether computer systems are involved. See https://pdfs.semanticscholar.org/d554/d933fd78e19d51d68ac4ea... and, more generally, https://en.wikipedia.org/wiki/Channel_capacity and https://en.wikipedia.org/wiki/Information_theory.

The field of Information theory effectively began with Claude Shannon. The same formalisms he developed are used outside computer science--linguistics, physics, microbiology, etc.