If sandals are the earliest form of footwear, then thong-style sandals are amongst the most enduring styles of sandals. The ancient Egyptians wore thongs as far back as 4000 B.C.E. But the appeal of the thong to Americans is much more recent: It derives from the Japanese zōri to which American soldiers took a liking after World War II. The soldiers brought them back to the United States, and by the 1960s, thongs had become popular amongst both men and women. Also called “flip-flops,” a word which derives onomatopoeically from the sound made when the sandals flap against the ground and the sole of the feet, thongs are regarded as the ultimate beach shoe and are ubiquitous in seaside cities such as Rio de Janeiro and Recife.