You see, after the gringos crushed the Hawaiian royalty and installed a fruit and sugar-extracting territorial government, immigrant workers arrived from Portugal, with their small, 4-string "braghina" guitars on their collective knee. Tuned somewhat differently from their more robust flamenco cousins, these smallish axes not only fit comfortably within a seaman's gig bag, but also provided a far from pompous sound. Elegant, and yet consumer-friendly, these guitars were one of the very few things the Eurotrash brought that - in the light of the fierce tropical sun of truth - seemed worthy of respect. Soon local and Portuguese craftsmen (such as the famous Nunes clan) were stamping out smaller versions, made of not-at-that-time-endangered tropical hardwoods. And, as you've probably guessed, the "braghina" evolved into the somewhat-more-compact "ukulele."
Since you're a smartypants, you know that "ukulele" does not mean "portuguese guitar," nor anything remotely similar. In fact, as you know from your doctoral dissertation, it means, "jumping flea." And there's an armload of apocrypha explaining how this patently preposterous name was adopted. The most common explanation is that a group of Hawaiians watched as Portuguese sailors played their braguinas, and described their finger movements as similar to "jumping fleas," (or, alternately, that they looked like they were scratching jumping fleas.)
Another version - according to famed guitar, banjo and uke collector, Akira Tsumura - holds that regular "army joe" Edward Purvis played his uke for King Kalakaua. People who saw Purvis play "transfered his nickname, which was 'ukulele,' to the small instrument he played."
Either way, the Hawaiians saw a good thing, and quickly assimilated the uke into their indigenous culture. The Panama Pacific International Exposition of 1915 featured Hawaiian music and hula dancing, and introduced the uke to the mainlanders. According to Pamela, of the raging West Coast uke monster band "Pineapple Princess," the uke was patented in the US in 1917, and, thereafter, we entered into "the ukulele Golden Age" of the early 1920's. Overnight, the uke was not only a mandatory accessory to the college career, but also a staple of vaudeville. Unfortunately, for most of the US, the uke was a fashion statement. So, while serious musicians such as Roy Smeck pushed the uke to its frontiers, and manufacturers experimented with hybrids (such as the banjolele and uk-e-lin) , the great masses forgot the instrument. Like most fads - such as oh, say, free speech - interest in the uke quickly declined.
For reasons as yet unexplained by historians, the US government recognized the decline in ukulele sales. Waiting until the best opportunity, Congress took it upon itself to declare war on Japan in 1942, to bring US servicemen into greater contact with this tremendously important cultural bulwark. Simultaneously, tone-deaf radio personality and domestic-violence connoiseur Arthur Godfrey brought the uke back with him from a mayhem-filled vacation to the territorial "protectorate" with his long-suffering spouse. Thereafter, the uke experienced its second flowering on the continental US vine, and, with the help of Elvis Presley (in BLUE HAWAII) and Ohta San, the ukulele became what it is today. Whatever that is.