Goodbye это сокращение от God be with you?

конечно

good-bye
salutation in parting, also goodbye, good bye, good-by, 1590s,
from godbwye (1570s), a contraction of God be with ye (late 14c.), influenced by good day, good evening, etc.
As a noun from 1570s. Intermediate forms in 16c. include God be wy you, God b'uy, God buoye, God buy, etc.