I think he means ctrl-r.

it’s actually called history-search-backward . it’s configured in /etc/inputrc or ~/.inputrc . if you type the first few characters of a command in your shells history, then type page-up (that key on the keyboard; if configured for page-up, which is common), it searches the most recent command that started that way. press again for the second recent. i’m using it so much, i got used to the thought process “i type this often -> lets stop typing and use page-up”. of course it can’t work with passwords 😅 i should pay more attention to what i’m doing