1859, American English, "saddle-girth," from Spanish cincha "girdle," from Latin cingulum "a girdle, a swordbelt," from cingere "to surround, encircle," from PIE root *kenk- (1) "to gird, encircle" (cognates: Sanskrit kankate "binds," kanci "girdle;" Lithuanian kinkau "to harness horses"). Replaced earlier surcingle. Sense of "an easy thing" is 1898, via notion of "a sure hold" (1888).
cinch (v.)
1866, "to pull in," from cinch (n.). Figurative meaning "make certain" is from 1891, American English slang. Related: Cinched; cinching.
实用例句
1. It sounds difficult, but compared to full-time work it was a cinch.
这听上去有难度，可是比起全职工作来，就是小意思了。
来自柯林斯例句
2. The first question is a cinch.
第一个问题是小菜一碟。
来自《权威词典》
3. He is a cinch to be boss of this firm some day.