This means that she hid herself with her clothing so that people would not recognize her. Traditionally, part of women's clothing were large pieces of cloth they wrapped themselves with. Alternate translation: "wrapped herself in her clothing so that people would not recognize her" (See: [[rc://en/ta/man/translate/figs-explicit]])
This can be stated in active form. Alternate translation: "Judah had not given her to Shelah as a wife" (See: [[rc://en/ta/man/translate/figs-activepassive]])