Why is Golgotha called the place of the skull?

John 19:17 - And He, bearing His cross, went out to a place called the Place of a Skull, which is called in Hebrew, Golgotha, [NKJV - parallel accounts in Matt. 27:33 and Mark 15:22] "Skull" or "a place of a skull" is the meaning of the Hebrew Word "Golgotha." According to Bible dictionaries, the site of Jesus' crucifixion was so named because in form it resembled the shape of a skull.