As with the Sign of the Cross, the Fingers Crossed action is used when the person feels the need for good luck, courage or protection. Most people accept that crossing fingers is a silly superstition, yet is it very common, in both action and speech. But when did it originate?
Crossing the first two fingers is a good luck sign recognised around the world. It is, however, not so common in Buddhist and Muslim cultures, suggesting that the symbol's origin is Christian and was imported to Asian countries along with other Western ideas, food, fashion, technology, karaoke (OK, maybe not karaoke).
We have no reliable evidence to support this, but one theory goes that during the various times when Christianity was illegal, the crossing of fingers was a secret sign for Christians to recognise each other. Yet whilst the Sign of the Cross has evolved into a good luck symbol and retained its Christian meaning, Fingers Crossed has lost any Christian connection.
This change of emphasis may have begun during the so-called 'Hundred Years War' between France and England (1337-1457). An archer would cross his first and second fingers, pray or wish for luck, and then draw back his longbow string with those same fingers. Maybe.
Another theory suggests that the sign pre-dates Christianity, when it was believed that benign spirits dwelt at the intersecting point of the cross, as in the Solar Cross. In Europe, the sign was made by two people; the first to make the wish and the second to support it. Linking their fingers firmly would squeeze and energize the spirits into beneficial action. Maybe.
In China, crossing the index and middle fingers is the sign for the number ten, which happens to coincide with the Chinese and Japanese written character for ten, which is . (The origin of this character is usually, yet erroneously, explained as two lines crossing to symbolise the four main directions, which in turn expressed the concept of completeness and by association all the fingers, i.e. ten. However, this seems a confused version of its actual origin. It derives from a depiction of a sewing needle with thread passing through the eye, and was used as a substitute for the more complex character , meaning 'hands together', i.e. ten fingers.)
The Roman numeral for ten (decem) is X, so one might expect that when deaf people communicate in sign language, crossed fingers spell the value ten or the alphabet letter X. But that is not the case. Deaf people sign ten with two actions (to mimic a '1' and a '0') and the letter X is signed with a curved index finger.
Crossed fingers in Swedish sign (Svenska Handalfabetet) do spell the letter 'X' but in other alphabets, the sign spells the letter R in English, Я (ya) in Russian (Cyrillic), (ra) in Japanese (hiragana), and the first half of (ss) in Korean (Hangul).
You see we were right with our comment at the top of this page: You can really bore the socks off people with this information.
And here's something else you can do with crossed fingers: The Aristotle Illusion
Cross your fingers, then touch a small spherical object such as a dried pea, and it feels like you are touching two peas. This also works if you touch your nose.
This is an example of what is called "perceptual disjunction". It arises because your brain has failed to take into account that you have crossed your fingers. Because the pea (or nose) touches the outside of both fingers at the same time - something that rarely happens - your brain interprets it as two separate objects.
Source: New Scientist