An American doesn’t need to be told that the meaning of the expression “to get cold feet” is to lose one’s nerve, to become craven.
The slang expression originated during my youth, probably in the early 1800’s, but, as has been the case from the earliest times, no one took the trouble to give it a date or to record the exact source.
We think it likely that its origin was a literal statement. Some wife, hearing a noise during the night, may have aroused her worthy but timorous husband to investigate the source.
He, poor wight, may have said that his feet were too cold, meaning, literally that his feet were so cold and the floor so icy that he couldn’t even chase a mouse. “Ya-a-ah,” she may have retorted, “you and your cold feet!”
And, if she were like some wives, she lost no time in passing the word around among all his friends that “Ed had such cold feet last night he couldn’t even get out of bed for fear a mouse would bite him.”