Crossing one's fingers for luck might seem like part of an ancient superstition, but the actual words "fingers crossed" did not appear in print anywhere before the mid 1920s! There may be a connection - from earlier times - with making an an inconspicuous 'sign of the cross' which, in religious terms, is a sort of a blessing. In other words, by doing the finger-crossing you're hoping God or the angels will ensure a fortunate outcome. People may have kept their fingers crossed centuries ago, but they certainly didn't say it!