Ye [are] the children of the LORD your God: ye shall not cut yourselves, nor make any baldness between your eyes for the dead. Deut.14:1 In our day when men are quick to have their unibrows waxed, this ancient perception of attractiveness might not be easily understood without some background.
Ancient Orientals admired eyebrows that met over the nose, presenting the appearance of a bow; and where nature denied them this ornament, they imitated it by artificial paint. This was removed in case of mourning, and the hair growing there naturally was plucked, in order to disfigure the face.
This is sometimes done now, and it appears that it was also done in ancient times; for Moses forbade the Hebrews to "make any baldness between their eyes for the dead."