What is the X in X-mas?
1850, American English, from American Spanish charqui "jerked meat," from Quechua (Inca) ch'arki "dried flesh."
"characterized by jerks," 1858, from jerk (v.1) + -y (2). Related: Jerkily; jerkiness.
Having the traits of a jerk: any jerky Joe (1940s+)