lenient (adj.) Look up lenient at Dictionary.com
1650s, "relaxing, soothing," from Middle French lenient, from Latin lenientem (nominative leniens), present participle of lenire "to soften, alleviate, mitigate, allay, calm," from lenis "mild, gentle, calm," which probably is from PIE root *le- "to leave, yield, let go, slacken" (source also of Lithuanian lenas "quiet, tranquil, tame, slow," Old Church Slavonic lena "lazy," Latin lassus "faint, weary," Old English læt "sluggish, slow," lætan "to leave behind"). Sense of "mild, merciful" (of persons) first recorded 1787. In earlier use was lenitive, attested from early 15c. of medicines, 1610s of persons.