I think the common terseness of many of the core suite of original unix tools actually reflects a strong focus on human, not machine, ergonomics. I still appreciate the speed and ease of typing them, and like many other aspects of the CLI, it's optimized for users who know it well and use it heavily. Once you're familiar with the names, it's not challenging to remove that mv = move, wc = wordcount, etc. Terminals of the era also still actually printed mechanically, so keeping command length short was a major ergonomic win for round trip speed.

As a sibling comment mentions, these commands were (are) commonly composed into scripts. As the name implies, however, a script is just a playbook for a series of commands to run. Given the terminals of the era, I'm sure short commands/variables/etc. were appreciated in scripts as well, but it seems to me that the primary motivation for optimizing input speed would be the use of these commands in an interactive environment.

A few examples of these core short program names: ls, cat, cp, rm, wc, uniq, cmp, diff, od, dd, tail, tr, etc.