Wastefulness comes from wasteful (from waste, via Old North French waster, from Latin vastare 'to lay waste') plus -ful and -ness. In current use it is a noun meaning "the quality of using resources carelessly or extravagantly". That sense is explained by the older material without requiring a speculative semantic step: the inherited or borrowed base supplies the field of meaning, while the English formation fixes its modern role. The suffix -ful marks possession or fullness of the quality named by the base. The surface form is compositional: its joined elements remain visible in the modern word. The historical chain includes Old French waster, Latin vastare, and Latin vastus. Related English forms include wasteful, waste, and wastrel. The word's history is thus visible in its construction: the components remain interpretable even after the whole expression has settled into a conventional English meaning.