From Knitting Lingerie Style:



This top evolved out of the body hugging wool jersey sleeveless bathing suits of the 1920s, which were ideal for the athletic, androgynous figure that modern fashions suited best.  The fabrication, however, left a lot to be desired, as the wool stretched when wet, and if not knitted firmly enough, the suits compromised a lady’s modesty in other ways.



This racerback tank was inspired by the tops of these suits, and it hints at the modern sports bra.  The elasticized cotton yarn alleviates any worry about stretching, and the mesh sides expose just the right amount of skin to be modest, yet intriguing.