Definition - a boastful and self-important person; a strutting little fellow
Once upon a time book titles were a touch more ... adventurous than they are today. Take, for example, the slim volume of songs and anecdotes the British publisher J. Fairburn foisted on an unsuspecting public at the turn of the 18th and 19th centuries: The Cockolorum songster, and convivial companion, for 1800: Being a collection of monstrous good, monstrous droll, and monstrous bad, songs, introduced by some eccentric anecdotes of my cousin, the noble grand cock. Also a few cockolorum sentiments. Yes siree, they don't title 'em like they used to...
In addition to describing a boastful person, cockalorum can be used in referring to the boastful talk (and also for the game of leapfrog. If cockalorum suggests a crowing cock, that's because the word probably comes from kockeloeren - an obsolete Dutch dialect verb meaning "to crow.”
The darned little cockalorum! If is weren’t business I’d have soaked the tar out of him. He would grudge the old soldiers their pensions!—has the nerve to talk to me about my cigars!
—The Los Angeles Times, 27 May 1916