What is the X in X-mas?
early 15c., vomiting, from Latin nausea "seasickness," from Ionic Greek nausia (Attic nautia) "seasickness, nausea, disgust," literally "ship-sickness," from naus "ship" (see naval). Despite its etymology, the word in English seems never to have been restricted to seasickness.
nausea nau·se·a (nô'zē-ə, -zhə, -sē-ə, -shə)
A feeling of sickness in the stomach marked by an urge to vomit.