bent (n.1) Look up bent at Dictionary.com
"mental inclination," 1570s, probably from earlier literal sense "condition of being deflected or turned" (1530s), from bent (adj.) "not straight" (q.v.).
bent (n.2) Look up bent at Dictionary.com
"stiff grass," Old English beonet, from West Germanic *binut- "rush, marsh grass" (cognates: Old Saxon binet, Old High German binuz, German Binse "rush, reed"), of unknown origin. An obsolete word, but surviving in place names (such as Bentley, from Old English Beonet-leah; Bentham).
The verdure of the plain lies buried deep
Beneath the dazzling deluge; and the bents,
And coarser grass, upspearing o'er the rest,
Of late unsightly and unseen, now shine
Conspicuous, and, in bright apparel clad
And fledg'd with icy feathers, nod superb.

[Cowper, "The Winter-Morning Walk," from "The Task"]
bent (adj.) Look up bent at Dictionary.com
"not straight," late 14c. (earlier ibent, c.1300, from past participle of bend (v.). Meaning "turned or inclined in some direction" is from 1530s, probably as a translation of Latin inclinatio. Meaning "directed in a course" is from 1690s. Figurative phrase bent out of shape "extremely upset" is 1960s U.S. Air Force and college student slang.