Cold Feet

The origin of the term itself has been largely attributed to American author Stephen Crane, who added the phrase, in 1896, to the second edition of his short novel, Maggie: A Girl of the Streets. The term is present in "Seed Time and Harvest" by Fritz Reuter published in 1862. Kenneth McKenzie, a former professor of Italian at Princeton University attributed the first use of the phrase to the play Volpone produced by Ben Jonson in 1605. The true origin and first usage of the phrase remains debated and unconfirmed as exemplified above.

A common use of the phrase is when people fear the commitment of marriage and get "cold feet" before a wedding ceremony. This pre-marital doubt or fear may manifest for a variety of reasons and sometimes cause the bride or groom to back out of a planned marriage. Original research on the "cold feet" phenomenon is very limited and warrants further studies. However, a four-year study conducted by UCLA researchers found feelings of pre-marital doubt or uncertainty about an impending marriage were associated with future marital problems and a viable predictor of divorce.

...
Wikipedia