rogue's cant 16c.-17c. for "a young girl of the vagrant class," of uncertain origin.
A Dell is a yonge wenche, able for generation, and not yet knowen or broken by the vpright man. ... [W]hen they have beene lyen with all by the vpright man then they be Doxes, and no Dells. [Thomas Harman, "A Caveat or Warning for Common Cursitors," 1567]