“Bated” breath is breath that is held, or subdued, because of some emotion.
“Bated” is simply a shortened form of “abated,” meaning “to bring down, lessen, depress, or stop.” Therefore, “to wait with bated breath” essentially means to hold your breath with anticipation.
The problem is that “bated” sounds exactly like “baited” and the two are often confused. Also, “bated” is mostly obsolete now and only used in the above construction. We all know what “bait” means. A fisherman baits his line in hopes of a big catch.
Mark Twain employed the word “bated” correctly in Tom Sawyer: “Every eye fixed itself upon him; with parted lips and bated breath the audience hung upon his words, taking no note of time, rapt in the ghastly fascinations of the tale.”
J K Rowling didn’t do so well. In an issue of one of the best selling books of all time, Harry Potter and the Prisoner of Azkaban, we have: “The whole common room listened with baited breath.” I hope her editor caught that before it went to print again.
Geoffrey Taylor, in his little poem Cruel, Clever Cat, 1933, used the confusion over the spelling of the word to good comic effect:
Sally, having swallowed cheese
Directs down holes the scented breeze
Enticing thus with baited breath
Nice mice to an untimely death
What about the phrase, “Don’t hold your breath!” This is usually used as mildly sarcastic humor, when applying it to an event you don’t expect to happen.
This US expression dates from the 1970s. The expression implies that it is not wise to stop breathing until a particular event occurs because you may be holding your breath for a very long time — maybe forever!
I know this last one well, since I often use it when somebody asks me things like when I’m going to rake the leaves, or do my income tax return, or make dinner.