I have apropos on my list for applications, but to be honest it’s more of a command than an actual program.
apropos (and its sibling whatis) are both part of man-db, and if you try to use apropos and get nothing from it, that’s probably because you need to run mandb first. (Hint, Arch users.)
Once it has a database of commands available to your system, apropos will help you pin down commands you can’t remember or can’t get right.
Notice that the output from the two commands is slightly different; if I understand it right, apropos is searching through man pages while whatis is only skimming descriptions.
apropos and whatis are both good commands for beginners to know, and even seasoned Linux nerds can rely on them at times. I know I do. 🙄
Inconsolation 