Emily Dickinson Lexicon

EARN'EST, n. [ern'est.]

1. Seriousness; a reality; a real event; as opposed to jesting or feigned appearance. Take heed that this jest do not one day turn to earnest. Sidney. And give in earnest what I begg'd in jest. Shak.
2. First fruits; that which is in advance, and gives promise of something to come. Early fruit may be an earnest of fruit to follow. The first success in arms may be an earnest of future success. The Christian's peace of mind in this life is an earnest of future peace and happiness. Hence earnest or earnest-money is a first payment or deposit giving promise or assurance of full payment. Hence the practice of giving an earnest to ratify a bargain. This sense of the word is primary, denoting that which goes before, or in advance. Thus the earnest of the spirit is given to saints, as a pledge or assurance of their future enjoyment of God's presence and favor.