The iliohypogastric nerve arises from the ventral ramus of L1, with a small branch from the ventral ramus of T12.  It passes infero-laterally through psoas major to emerge from its upper lateral border with or above the ilio-inguinal nerve.  It passes over the anterior surface of quadratus lumborum to pierce the transversus abdominis muscle above the iliac crest.  It descends antero-inferiorly between the transversus abdominis and internal oblique muscles where it divides into lateral and anterior cutaneous branches.

The lateral cutaneous branch pierces the internal and external oblique muscles above the iliac crest to terminate in the postero-lateral gluteal skin.  The anterior cutaneous branch passes between the transversus abdominis and internal oblique muscles.  It pierces the internal oblique muscle medial to the anterior superior iliac spine and the external oblique aponeurosis above the superficial inguinal ring, to terminate in the suprapubic skin.  

Supply
The iliohypogastric nerve supplies the transversus abdominis and internal oblique muscles and postero-lateral gluteal and suprapubic skin.