mid-13c., from Old French solstice (13c.), from Latin solstitium "point at which the sun seems to stand still," especially the summer solstice, from sol "the sun" (from PIE root *sawel- "the sun") + past participle stem of sistere "stand still, take a stand; to set, place, cause to stand," from PIE *si-st-, reduplicated form of root *sta- "to stand, make or be firm." In early use, Englished as sunstead (late Old English sunstede).
