The first produce or result, notably firstborn offspring.
And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the Lord had respect unto Abel and to his offering:1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC, Genesis 4:4:
The seasons bring the flower again, And bring the firstling to the flock; And in the dusk of thee, the clock Beats out the little lives of men.1850, [Alfred, Lord Tennyson], “Canto II”, in In Memoriam, London: Edward Moxon, […], →OCLC:
2
The first of a class or kind.
3
The thing first thought or done.
From this moment the very firstlings of my heart shall be the firstlings of my hand.c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act IV, scene i]:
All the firstling males that come of thy herd and of thy flock thou shalt sanctify unto the Lord thy God: thou shalt do no work with the firstling of thy bullock, nor shear the firstling of thy sheep.1611, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], →OCLC, Deuteronomy 15:19: