Origins
The word 'genre' entered English from French in the 1770s, initially as a term in art criticism referring to paintings that depicted scenes of everyday life rather than mythological, historical, or religious subjects. Its French source, 'genre,' meant simply 'kind' or 'sort,' and derived from Old French 'gendre,' which descended from Latin 'genus' (birth, origin, kind, race). At the deepest recoverable level, it traces to the Proto-Indo-European root *ǵenh₁-, meaning 'to beget' or 'to give birth.'
This PIE root is one of the most productive in the entire Indo-European family. In Latin alone, it generated 'genus' (kind), 'gens' (clan, race), 'genius' (innate spirit, later intellectual brilliance), 'generāre' (to beget, whence English 'generate'), 'generōsus' (of noble birth, whence 'generous'), 'gentilis' (of the same clan, whence 'gentle' and 'gentile'), and 'ingenium' (inborn talent, whence 'engine' and 'ingenious'). Through Greek, the root produced 'genesis' (origin), 'genos' (race, kind), and the combining form '-gen' used in modern scientific terms like 'oxygen' (literally 'acid-begetter') and 'hydrogen' ('water-begetter').
On the Germanic side, the same PIE root *ǵenh₁- produced a completely different-looking family of words. The initial palatalized *ǵ- became *k- in Proto-Germanic by Grimm's Law, yielding Old English 'cynn' (kind, race, family), which became Modern English 'kin.' The words 'kind' (both the noun meaning 'type' and the adjective meaning 'benevolent'), 'king' (originally 'leader of the kin'), and 'kindergarten' (via German, literally 'children's garden') all descend from this same root. So 'genre' and 'kin' are doublets — words from the same ultimate source that entered English by different routes and at different times.
Development
In French, 'genre' had long served as the ordinary word for 'kind' or 'type.' Its adoption into English was narrow and specific: eighteenth-century art critics needed a label for the Dutch and Flemish tradition of painting domestic and tavern scenes, and they borrowed the French term 'genre' for this purpose. A 'genre painting' by Vermeer or Jan Steen depicted ordinary people doing ordinary things, in contrast to the grand subjects — gods, battles, kings — that the academic hierarchy of painting considered more elevated.
The word's semantic expansion began in the nineteenth century, when literary critics applied it to categories of fiction (the novel, the romance, the gothic tale) and then to subcategories within those forms. By the twentieth century, 'genre' had become the default term for any recognized category in any art form: genre fiction, genre film, musical genres. The irony is that 'genre painting' originally named the lowest rung of the academic ladder, while today the concept of genre is so ubiquitous that no art form can be discussed without it.
The pronunciation of 'genre' in English reflects its French origin. Most English speakers preserve the French nasal vowel or approximate it, saying /ˈʒɑːnɹə/, with the French 'zh' sound at the beginning. This makes 'genre' one of a cluster of French loanwords — alongside 'rouge,' 'beige,' 'garage,' and 'mirage' — that brought the /ʒ/ phoneme into English, a sound that Old English lacked entirely.
Latin Roots
Modern biology adopted the Latin form 'genus' directly, using it as the fundamental rank in Linnaean taxonomy between family and species. When Linnaeus published his Systema Naturae in 1735, he chose 'genus' precisely for its meaning of 'kind' or 'birth-group.' So in biology, 'genus' classifies organisms by shared descent, while in the arts, 'genre' classifies works by shared characteristics — both reflecting the root sense of *ǵenh₁-: things that are born together, that share an origin.