diastole (n.)

"normal rhythmic relaxation of the heart" (alternating with the systole), 1570s, from medical Latin diastole, from Greek diastole "drawing asunder, dilation," from diastellein, from dia "through; thoroughly, entirely" (see dia-) + stellein "to set in order, arrange, array, equip, make ready," from PIE *stel-yo-, suffixed form of root *stel- "to put, stand, put in order," with derivatives referring to a standing object or place. Related: Diastolic.