つと.める 
() toil
つとめて (adv) (1) as much as possible, diligently, (exp) (2) make an effort!, work hard!
つとめる (v1,vt) to endeavor (endeavour), to try, to strive, to make an effort, to exert oneself, to be diligent
どりょく (n,vs) great effort, exertion, endeavour, endeavor, effort

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Etymologies: 中文字譜 : 説文解字