Kumbayah is a uniquely African-American contribution to American English.
Kumbayah is a Gullah pronunciation of the phrase "Come by here" (or "come by yah", 'yah' being
a West African form of 'here'.)
turned into an ironic term by overusage and misinterpretation by the mainstream culture. However, it's actually a call
to God to visit
the singer. "Kumbayah my lord" means 'come by here, my lord".