"become steep or more steep," 1827, from steep (adj.) + -en (1). Related: Steepened; steepening.
Entries linking to steepen
steep adj.
"having a sharp slope," Old English steap "high, lofty; deep; prominent, projecting," from Proto-Germanic *staupa- (source also of Old Frisian stap "high, lofty," Middle High German *stouf), from PIE *steup-, extended form of root *(s)teu- (1) "to push, stick, knock, beat," with derivations referring to projecting objects (source also of Greek typtein "to strike," typos "a blow, mold, die;" Sanskrit tup- "harm," tundate "pushes, stabs;" Gothic stautan "push;" Old Norse stuttr "short"). The sense of "precipitous" is from c. 1200. The slang sense "at a high price" is a U.S. coinage first attested 1856. Related: Steeply; steepness. The noun meaning "steep place" is from 1550s.
-en 1
word-forming element making verbs (such as darken, weaken) from adjectives or nouns, from Old English -nian, from Proto-Germanic *-inojan (also source of Old Norse -na), from PIE adjectival suffix *-no-. Most active in Middle English and early modern English, hence most verbs in -en are comparatively recent.