英语词源字典 - 在线词源网站

brae (n.): "steep slope," in northern England especially "the sides of a hill," early 14c., from Scottish, "slope, river bank," from Old Norse bra "eyelash," cognate with Old English bræw "eyelid," German Braue "eyebrow" (see brow). "The word must have passed through the sense of 'eye-brow' to 'brow of a hill', supercilium (cf. OE. eaghill 'eye-hill'=eyebrow)" [OED].
cliff (n.): Old English clif "rock, promontory, steep slope," from Proto-Germanic *kliban (cognates: Old Saxon clif, Old Norse klif, Middle Dutch klippe, Dutch klip, Old High German klep, German Klippe "cliff, promontory, steep rock").

Clift has been a variant spelling since 15c. and was common in early Modern English, influenced by or merged with clift, a variant of cleft (n.). Cliff-dweller first attested 1889, American English.
escarp (n.): "steep slope," especially as part of a fortification, 1680s, from French escarpe (16c.), from Italian scarpa (see scarp).
escarpment (n.): 1802, from French escarpment, from escarper "make into a steep slope," from escarpe "slope," from Italian scarpa (see scarp). Earlier in same sense was escarp.
gradient (n.): "steep slope of a road or railroad," 1835, principally in American English, probably from grade (n.) by analogy of quotient, etc. [OED]. It was used 17c. as an adjective, of animals, "characterized by walking;" in that case it is probably from Latin gradientem, present participle of gradi "to walk."
scarp (n.): "steep slope," 1580s, from Italian scarpa "slope," probably from a Germanic source, perhaps Gothic skarpo "pointed object," from Proto-Germanic *skarpa- "cutting, sharp" (cognates: Middle High German schroffe "sharp rock, crag," Old English scræf "cave, grave"), from PIE *(s)ker- (1) "to cut" (see shear (v.)).