The word 'steeliness' is a relatively modern English formation, built upon the concrete noun 'steel'. 'Steel' itself has ancient Germanic origins, traceable to the Proto-Germanic 'stahliją', which referred to the durable metal alloy. The abstract noun-forming suffix '-ness' is one of the most productive in English, descending directly from the Old English '-nes', used to create nouns indicating a state, condition, or quality. By combining the tangible, robust image of 'steel' with the abstracting force of '-ness', 'steeliness' was coined to metaphorically project the physical properties of the metal—such as hardness, strength, and resilience—onto human character, demeanor, or resolve, encapsulating an unyielding and formidable quality.

Structure: steel (hard metal) + iness (noun suffix denoting quality) 'steel' (from Old English 'stēle', 'stȳle', meaning the hard metal alloy; functional role: root/base noun). 'iness' (a compound suffix formed from '-y' (adjective-forming) + '-ness' (noun-forming), ultimately from Old English '-nes'; functional role: suffix forming an abstract noun denoting a state or quality).