Context

This line is written by John in John 19:30.

Here John is describing the death of Jesus on the cross. It's pretty self-explanatory, and "gave up the ghost" is a pretty elegant and imaginative way to describe dying.

Where you've heard it

"Give up the ghost" is one of probably a million ways to say "die." In the dictionary of death, it falls somewhere between and "go to glory" and "kick the bucket."

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

This is no more pretentious than saying someone "cashed in their chips," "croaked," or "was delivered to Davy Jones' locker."