Meaning

noun any of various long-tailed primates (excluding the prosimians)

noun one who is playfully mischievous

verb play around with or alter or falsify, usually secretively or dishonestly

originUncertain: * May be derived from monk + -ey (diminutive suffix), * or borrowed from Middle Low German Moneke, the name of the son of Martin the Ape in Reynard the Fox (which may represent an unattested colloquial Middle Low German *moneke, *moneken), itself of uncertain origin: ** Possibly derived from a Romance term represented by Late Middle French monne (whence Modern French mone (“monkey”))…

Etymology from Wiktionary, CC BY-SA 3.0