Old English gyrdel "belt, sash, cord drawn about the waist and fastened," worn by both men and women, common Germanic (cognates: Old Norse gyrðill, Swedish gördel, Old Frisian gerdel, Dutch gordel, Old High German gurtil, German Gürtel "belt"), related to Old English gyrdan "to gird," from PIE root *gher- (1) "to grasp, enclose" with instrumental suffix -el (1). Modern euphemistic sense of "elastic corset not extending above the waist" first recorded 1925. Originally a belt to secure the clothes, also for carrying a purse, a weapon, keys, etc.
"encircle with a girdle," 1580s, from girdle (n.). Meaning "to cut off a belt of bark around a trunk to kill a tree" is from 1660s, especially in North America. Related: Girdled; girdling.