(A). 500. (See Marygold.)
= the Devil; an imp of mischief. Hence, a meddlesome child is spoken to as “you little monkey;” and is called “a regular imp,” or “imp of mischief.” The allusion is to the old drawings of devils, with long tails and monkey ugliness.
To get (or have) one's monkey up. To be riled. Here the allusion is also to the devil or evil spirit in man; he will be “in a devil of a temper.” Even taken literally, monkeys are extremely irritable and easily provoked.
in sailor language, is the vessel which contains the full allowance of grog. Halliwell (Archaic Dictionary) has-
“Moncorn, `Beere corne, barley bygge, or moncorne.' ”- (1552.)
To suck the monkey. Sailors call the vessel which contains their full allowance of grog “a monkey.” Hence, to “suck the monkey” is surreptitiously to suck liquor from a cask through a straw. Again, when the milk has been taken from a cocoanut, and rum has been substituted, “sucking the monkey” means drinking this rum. Probably “monkey” in all such cases is a corruption of moncorn (ale or beer). (See Marryat's Peter Simple.) (See Monkey Spoons.)
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894