What does John 19:8 mean?

In Pilate's encounter with Jesus, it's clear he recognizes much of what's really happening. This is a personal feud on the part of Israel's religious leaders (Matthew 27:18; John 11:48–53). Jesus is no political revolutionary (John 18:36–38). Other gospel writers note that Pilate's wife is also worried about the prospect of harming Jesus (Matthew 27:19). When Pilate has Jesus brutally whipped and mocked, he thinks that might appease the mob (John 19:1–5). Instead, they demand His crucifixion (John 19:6).

Demanding such a brutal death seems to shock Pilate. Jerusalem's religious leaders explain that Jesus has committed blasphemy, something for which they want Him to suffer (John 19:7). They use the phrase "Son of God," accurately accusing Jesus of using that title (Matthew 26:63–66). What they probably don't expect is that this association only makes Pilate more reluctant.

Roman mythology included a host of demigods: men with one divine parent. To abuse a demigod could bring the wrath of that god. Saying that Jesus claims to be "Son of God" concerns Pilate enough to ask more questions, starting with "where are you from?" as shown in the next verse (John 19:9).