Discussion Forum—A Way with Words, a fun radio show and podcast about language

The meaning of fast as secure or hard to move is older than it meaning speedy.   I think it is probably going out of common usage but think of "color fast" or "fasten."   I think it is related in some way to being speedy but without looking it up, I can't think how it is.

This of "tie it fast", or "make the boat fast to the piling".   Someone who is fast asleep is probably going to be difficult or impossible to waken.

Never thought of "fasten" before, though.

We also say "sound asleep", which is similar.