So the thigh of a rider on horseback would be covered by a loose girdle, on which his name might be embroidered (Revelation 19:16). The hollow of the thigh (Genesis 32:25) is the hip-socket or the groin. See also HIP.
Dawn, from an Old English verb dagian: to become day, is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in the atmosphere, when the centre of the Sun's disc reaches 18Â° below the horizon.
The morning in this verse is the breaking forth or dawning of light to begin a new day. The morning or dawn is the other dividing period, this time separating darkness (night) from light (day). It is the result of Yahweh having divided between the light and the darkness (verse 4b).