The word 'supple' entered English in the late 13th century from the Old French 'souple', meaning "pliant, flexible, obedient." The Old French term itself evolved from the Latin adjective 'supplex', which meant "submissive, humbly begging," and was formed from 'sub' (under) and the root of 'plicare' (to fold). The literal sense of "bending under" or "folding oneself" in submission evolved into the core physical meaning of being easily bent or flexible. Over time, the word's connotations softened, losing much of its original association with subservience and emphasizing graceful physical adaptability, which later extended to describe mental agility and adaptability.

The word 'supple' is a simplex word derived as a whole from Latin via French. Its core morpheme 'supple-' does not have separable, meaningful sub-parts within modern English spelling that align with distinct semantic units.