Breathing that is subdued because of some emotion or difficulty.
Which is it - bated or baited? We have baited hooks and baited traps, but bated - what's that? Bated doesn't even seem to be a real word, where else do you hear it? Having said that, 'baited breath' makes little sense either. How can breath be baited? With worms?
There seems little guidance in contemporary texts. Search in Google and you'll find about the same number of hits for 'baited breath' as 'bated breath'. In one of the best selling books of all time, Harry Potter and the Prisoner of Azkaban (whose publisher could surely have afforded the services of a proof-reader), we have:
"The whole common room listened with baited breath."
As so often is the case, help is found in the writings of the Bard. The earliest known citation of the phrase is from Shakespeare's Merchant of Venice, 1596:
What should I say to you? Should I not say
'Hath a dog money? is it possible
A cur can lend three thousand ducats?' Or
Shall I bend low and in a bondman's key,
With bated breath and whispering humbleness, Say this;
'Fair sir, you spit on me on Wednesday last;
You spurn'd me such a day; another time
You call'd me dog; and for these courtesies
I'll lend you thus much moneys'?
'Bated' is simply a shortened form of 'abated', meaning 'to bring down, lower or depress'. 'Abated breath' makes perfect sense and that's where the phrase comes from.
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.
See other phrases and sayings from Shakespeare.