Soundness comes from sound (healthy, whole) + -ness. This sound derives from Old English sund, gesund ('healthy, safe, whole'), from Proto-Germanic *gasundaz ('healthy, sound'). The historical chain includes Old English gesund and Proto-Germanic *gasundaz. The quoted older senses, "healthy, safe, whole" and "healthy, sound", supply the semantic anchors for soundness. The formation is best read as suffixal and borrowed: the word soundness carries its older form-history into a compact English lexical shape. In present English it is used as a noun, "the quality of being healthy, solid, or logically valid". Related English forms include sound. The result is a noun whose etymology preserves both the older form and the later English specialization.