monotony (n.) Look up monotony at Dictionary.com
1706, originally in transferred sense of "wearisome, tiresome," from French monotonie (1670s), from Greek monotonia "sameness of tone, monotony," from monotonos "monotonous, of one tone," from monos "single, alone" (from PIE root *men- (4) "small, isolated") + tonos "tone," from PIE root *ten- "to stretch." Literal sense of "sameness of tone or pitch" in English is from 1724.