The cross is an ancient symbol in many cultures and religions . It is closely linked , of course , with the Christian church . The cross was also a sacred symbol to the Egyptians and to the Aztecs in Mexico . Scandinavian cultures also used crosses to mark the edges of their territory . Today , we use the word “cross ” in many expressions that seem to have little direct connection to religious beliefs . We often just cross two of our fingers to wish them luck . But , more often , just saying the expression is believed to be enough to help bring success . Crossing the fingers when making a wish may be a tradition many hundreds of years old . It probably has its roots in the ancient Christian belief that making the sign of the cross would keep away evil spirits and bad luck . Years ago , children would cross their fingers when they were telling a small lie . However , over the years , children most likely have unhappily discovered that crossing their fingers offers no such protection . Perhaps that explains why most children these days do not cross their fingers for luck . Now , some children may use another old expression -- cross my heart . Children might say this when they want to prove that they are really and truly telling the truth about something . A child may make an “X ” over their heart with their finger while saying it . They don't say this anymore . No one does . In fact , this is the first time that I have heard of this expression . But I have heard it said this way : “Cross my heart and hope to die and stick a needle in my eye .” Now , besides children protesting their innocence -- we use the word “cross ” in many other ways . To double cross does not mean to cross yourself twice . This means to betray someone , especially someone who trusts you . “Double-crosser ” is not a name you want . To have your wires crossed is different . This simply means two people fail to understand each other . There is no purposeful or planned attempt to betray one another . Merriam Webster's dictionary says that this expression is used between two people . This is because the origin of this expression comes from the early days of using the telephone . When two wires came in contact with each other , phone conversations could be mixed up . However , we also use this common expression to mean someone simply made a mistake -- all on their own . For example , “I must have gotten my wires crossed . I thought the party was on Saturday , not Sunday .” Now , there is no case of mistaken information if you are at cross purposes with someone . This expression began in the 1660s . It means that different goals are working against each other . To understand how to better use these [and other ] expressions , let's hear them used in a short story . Let's say you work at a large book publishing company as an editor . You and the writer want to sell many books . The goal of the company is the same – publish good books and sell as many as possible . But recently , conditions in the book publishing world have not been great – far from it . Book sales have been down . Each department has been feeling the pressure and each has its own idea of how to help . The public relations (PR ) department wants to spend more money on author tours and book release parties . But the business office sees these activities as unnecessary expenses . So , their goal is to cut them . These two departments are definitely working at cross purposes . You probably feel that every time you cross paths with them . Someone in the business department is always trying to convince you of their side . The same is true with the PR department . You want to stay out of it . So , you try to not cross their paths . One day , as you are trying to avoid crossing paths with your co-workers , something crosses your mind . Suddenly and without forethought , you think of a way to make both departments happy . You tell your friend in PR your idea and he loves it . Then you tell another friend in the business office your idea . She loves it , too . However , they both get their wires crossed . They didn't completely understand all the details of your idea . So , when they come together in a meeting to discuss the idea , they realize it is not exactly what they had thought . They are not happy . They become cross with each other -- and with you ! They both think you tried to double cross them ! For several weeks , both departments are angry with each other and with you . It causes you much worry and concern . This is a heavy cross to bear . You lose sleep and work becomes unbearable . But you still think you can clear it up with a simple explanation . And that is what you do . One day , you invite both of your friends to lunch . You explain that they didn't understand your idea fully . You even cross your heart and hope to die if you are lying . Your explanation -- and this silly childhood expression -- is enough to prove to them that you are telling the truth . They apologize and realize that your idea can still work . You say to them , “That's up to you two ! I'll keep my fingers crossed for the both of you . But now , I am going back to what I do best for the company -- editing stories .” But we'll be back next week with another new story explaining common expressions in American English . I cross my heart .