earnest (adj.) Look up earnest at Dictionary.com
from Old English eornoste (adj.) "zealous," or from Old English noun eornost "seriousness, serious intent" (surviving only in the phrase in earnest), from Proto-Germanic *ern "vigor, briskness" (cf. Old Saxon ernust, Old High German arnust "seriousness, firmness, struggle," German Ernst "seriousness;" Gothic arniba "safely, securely;" Old Norse ern "able, vigorous," jarna "fight, combat"). The proper name Ernest (literally "resolute") is from the same root. Related: Earnestly; earnestness.