1580s, "made of steel," from steel (n.) + -y (2). Figurative meaning "hard and cold as steel" is from c. 1500. Related: Steeliness.
Entries linking to steely
steel n.
modified form of iron with a small portion of carbon, not found in nature but known in ancient times, Old English style "steel," from noun use of Proto-Germanic adjective *stakhlijan "made of steel" (source also of Old Saxon stehli, Old Norse, Middle Low German stal, Danish staal, Swedish stål, Middle Dutch stael, Dutch staal, Old High German stahal, German Stahl), related to *stakhla "standing fast," from PIE *stek-lo-, from root *stak- "to stand, place, be firm" (see stay (n.1)). The notion is perhaps "that which stands firm." No corresponding word exists outside Germanic except those likely borrowed from Germanic languages.
As an adjective from c. 1200 (Old English used stylen "*steel-en." Steel wool is attested from 1896. Steel drum is from 1952.
-y 2
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy). Adjectives such as hugy, vasty are artificial words that exist for the sake of poetical metrics.