backboneless comes from backbone + the privative suffix -less, extending the figurative sense of backbone as 'firmness of character'. Morphologically, the word is transparent: -less is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the adjective sense is "lacking firmness of character; spineless", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as backbone, back, bone, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old English bæc, Old English bān, which anchor the explanation in named linguistic material.