Étude comes from the French word meaning study. An étude is a short instrumental piece, usually for piano, used for practicing particular musical skills and usually requires considerable technical dexterity. The spectrum of the étude ranges from the private and purely mechanical exercises of Czerny and Hanon to concert performance pieces of Liszt and Chopin[1]. The piano étude was popularized in the early 19th century as the piano became more popular and affordable. Composers who wrote in this era include Clementi, Hummel and Henselt[2]. As the century progressed, the étude turned to the public scene into concert performance repertoire. Liszt and Chopin are among some of the first composers credited for this shift. Paganini famously wrote solo violin étude in this era. In the 20th century, études continued to be written for professional and amateur use, most notably by Skryabin, Rakhmaninov, Prokofiev, Bartók, and Ligeti[3]. Études continue to be composed and performed today although unparalleled to the technical difficulties of 19th century concert etudes.
[1] The Oxford Companion to Music: étude
[2] The Oxford Companion to Music: étude
[3] The Oxford Companion to Music: étude