variant of -orama, occurring as the final element in compounds when the first element is disyllabic and does not end in -r, used so that the entire word maintains the same number of syllables as panorama: Cinerama; telerama.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
noun suffix meaning "sight, view, spectacular display or instance of," 1824, abstracted from panorama (q.v.), ultimately from Greek horama "sight, spectacle, that which is seen."
Online Etymology Dictionary, © 2010 Douglas Harper