skittish (adj.) Look up skittish at Dictionary.com
early 15c., "very lively, frivolous," perhaps from Scandinavian base *skyt- (stem of Old Norse skjuta "to shoot"), from PIE root *skeud- "to shoot, to chase, to throw, to project" (see shoot (v.)). Sense of "apt to run" first recorded c.1500, of horses.