What does bucko mean?

bucko meaning in Etymology Dictionary

term of target, originally (1883) nautical along with a sense of "swaggering, domineering other." Probably from dollar (n.1) when you look at the slang feeling of "a blood or option character."There have been in London divers lodges or communities of Bucks, formed in imitation regarding the Free Masons: one happened on Rose, in Monkwell-street, concerning the year 1705. The president is styled the Grand Buck. ["Dictionary of the Vulgar Tongue," 1811]