Linguistically the viola is the basic instrument of the so-called violin family. A violin is literally a small viola. A violoncello is small violone, while a violone is a very large viola. A modern double bass is basically a violone. The term “viola” is derived from the medieval Latin “vitula,” which may be related to vitularia: “to celebrate joyfully,” from Vitula, Roman goddess of joy and victory. (Why not?) The word “fiddle” likely derives from the same root as does the Spanish vihuela, which is a guitar, not a viola. (However,“guitar” is derived from the Greek “kithara,” a type of lyre.) The flowers called “violets” are diminutive of viola in the species Violaceae.
A viola held by the arms is a viola da braccio (viola of the arms – the word “broccoli” comes from the same root), and a viola held by the legs is a viola da gamba (viola of the legs – “gams” is a slang term for legs).
Due to their size, it takes strength and endurance to play a viola. Most historic violas have been cut down (especially in the depth of the body) to make them more wieldy.
None of this really addresses the structural differences between violin family instruments and the violas da gamba, which question is further clouded by the fact that modern double basses are basically violones of the latter family (at least in tuning and often in form and bowing technique).
This is the viola on which my father made his living most of his life. By Gagliano 1775
“I would give you some violets, but they withered all when my father died…”
-Hamlet