What is the X in X-mas?
"a leap, a bound," 1620s, from Latin saltationem (nominative saltatio) "a dancing; dance," noun of action from past participle stem of saltare "to hop, dance," frequentative of salire "to leap" (see salient (adj.)).
saltation sal·ta·tion (sāl-tā'shən, sôl-)
The act of leaping, jumping, or dancing.
Discontinuous movement, transition, or development; advancement by leaps as of a disease or physiologic function.
A single mutation that drastically alters the phenotype.