hard-working (adj.)

Old English hearde "firmly, severely," from hard (adj.). Meaning "with effort or energy, with difficulty" is late 14c.

late 14c., "active, busy," present-participle adjective from work (v.). From 1630s as "engaged in physical toil or manual labor as a means of livelihood." Working class is from 1789 as a noun, 1839 as an adjective. Working-day is from late 15c.; working man is by 1816.