A diminutive of Hob, pet form of Robert, the word hobby was originally used to denote a small horse; the term hobby horse came to denote a child’s toy consisting of a stick with a model of a horse’s head at one end, and, by the mid-17th century, hobby horse had come to denote a favourite occupation or topic, which was compared to the riding of a toy horse.
The first two volumes of The Life and Opinions of Tristram Shandy, Gentleman (first published in 1759), by the Irish novelist Laurence Sterne (1713-68), popularised this later acceptation of the term hobby horse, which the narrator uses to characterise Uncle Toby; for instance, chapter 23 of volume 1 concludes with:
(3rd edition – London, 1760)
In giving you my uncle Toby’s character, I am determin’d to draw it by no mechanical help whatever;—nor shall my pencil be guided by any one wind instrument which ever was blown upon, either on this, or on the other side of the Alps;—nor will I consider either his repletions or his discharges,—or touch upon his Non-Naturals;—but, in a word, I will draw my uncle Toby’s character from his Hobby-Horse.
As well as being very popular in Britain, Laurence Sterne’s novel enjoyed a considerable vogue in other European countries. In particular, the French translation by Joseph-Pierre Frénais (died 1788), La vie et les opinions de Tristram Shandy (first published in 1776) gave to French dada, a child’s noun for horse, the figurative meaning of favourite pastime or pet idea (cf. note). This is the translation by Frénais of the above-quoted passage from Tristram Shandy:
Pour vous décrire le caractere de mon oncle M. Tobie Shandy […] suis-je bien résolu de n’emprunter le secours d’aucune machine pour le peindre.—Je ne souffrirai point que mon pinceau se laisse diriger par aucun des instruments à vent qui ayent jamais soufflé en-deçà ou au-delà des Alpes.—Je ne déroberai rien à son Médecin.—Mais son cheval de course, son dada, son cher califourchon, ou, pour parler sans figure, ses caprices, c’est là ce qui me servira à le caractériser.
In this French translation, “son cheval de course, son dada, son cher califourchon, ou, pour parler sans figure, ses caprices” means “his race horse, his dada, his dear califourchon, or, to speak wihout figure [of speech], his caprices”.
It is interesting to remark that it was Frénais’s translation that gave to the French word califourchon the figurative sense of pet hobby—a meaning, however, that has not survived, the word being now only used as it originally was, that is, in à califourchon, meaning astride.
However, the French phrase être à cheval sur quelque chose, meaning to sit astride something (from à cheval, on horseback), is used figuratively to mean to be a stickler for something.
The noun Dada, with a capital D, designates an early-20th-century movement in art, literature, music and film, active most notably in Europe and the United States, repudiating and mocking artistic and social conventions and emphasising the illogical and absurd. This movement was founded in Zurich during the First World War by a group of international, and multilingual, artists, writers and performers, among whom the Romanian-born French poet Tristan Tzara (Samuel Rosenstock – 1896-1963).
The name first appeared in print in Cabaret Voltaire (1916): on page 5, in an editorial in German by the German author Hugo Ball (1886-1927), dated 15 May, where it appears as the proposed title for a periodical review which was first published later in the same year, and on page 31, in a dialogue in French and German by the German author and psychoanalyst Richard Huelsenbeck (1892-1974) and Tristan Tzara.
According to two accounts, both dating from 1916, by Richard Huelsenbeck and Hugo Ball, the name was originally chosen at random from a dictionary, where the headword was French dada; however, the name was adopted with conscious reference to the underlying syllables, perceived as ultimately meaningless.—source: Oxford English Dictionary – 3rd edition, 2016