The musical instrument called ukulele originated in the 19th century as a Hawaiian interpretation of the cavaquinho or braguinha and the rajão, small guitar-like instruments taken to Hawai by Portuguese immigrants It gained great popularity elsewhere in the United States during the early 20th century, and from there spread internationally. The tone and volume of the instrument varies with size and construction. Ukuleles commonly come in four sizes: soprano, concert, tenor, and baritone.

The cavaquinho is a small string instrument of the European guitar family with four wire or gut strings. It is also called machimbo, machim, machete (in the Portuguese Atlantic islands and Brazil by Paulinho da Viola), manchete or marchete, braguinha or braguinho.The most common tuning is D-G-B-D (from lower to higher pitches); other tunings include D-A-B-E (Portuguese ancient tuning, made popular by Júlio Pereira) and G-G-B-D and A-A-C#-E. Guitarists often use D-G-B-E tuning to emulate the highest four strings of the guitar. The G-C-E-A tuning is sometimes used to emulate the soprano/tenor ukulele, an instrument developed from the cavaquinhos brought to Hawai'i by Portuguese immigrants in the late 19th century.     wikipedia

The cavaquinho is also found in other places where the Portuguese left an imprint, namely Cape Verde (Cesaria Evora) and the USA (especially Hawaii), and became an important part of the popular music of those places.  

Now, I think what may have been a source of interest and use of this instrument so unique and ancient, was the fact that was offered a cavaquinho (ukulele) to the artist Eddie Vedder, when their tour of Lisbon in 2006. I must say that the initiative of the album Ukulele Songs represents an evolution and a remarkable development in the artist's career Eddie Vedder, your search for the origins of the universal nature of music.However it is sad that did not have the courage to go one step further and integrate in album a song (adapted)of traditional Portuguese song repertoire.

So, by way of remembrance for E.Vedder, here's the extraordinary performance of the master-ukellele Julio Pereira, in Porto. Casa da Música. 2008, the song "Faro Luso", unfortunately, the sound quality appears in the video, does not allow fully realize the full potential of this fantastic musician (of election), and can be seen in the original album "Geographies (2007).": 

Meow. Eddie makes me purrrrrrrrrrrrrrrrrrr.