What is the X in X-mas?
"sudden change of mind," 1660s, from French caprice "whim" (16c.), from Italian capriccio "whim," originally "a shivering," possibly from capro "goat," with reference to frisking, from Latin capreolus "wild goat" (see cab). But another theory connects the Italian word with capo "head" + riccio "curl, frizzled," literally "hedgehog" (from Latin ericius). The notion in this case would be of the hair standing on end in horror, hence the person shivering in fear.