"Eternal in the Bible is really about not having an end, not about not having a beginning." I have been reading the Bible for years and never once came across anything remotely suggesting that.
This question is trivially easy to answer. Doing a search through the King James Version for eternal life turns up the following:
BibleGateway - Keyword Search: eternal life
Matthew 19:16
And, behold, one came and said unto him, Good Master, what good thing shall I do, that I may have eternal life?
Matthew 25:46
And these shall go away into everlasting punishment: but the righteous into life eternal.
Mark 10:17
And when he was gone forth into the way, there came one running, and kneeled to him, and asked him, Good Master, what shall I do that I may inherit eternal life?
Mark 10:30
But he shall receive an hundredfold now in this time, houses, and brethren, and sisters, and mothers, and children, and lands, with persecutions; and in the world to come eternal life.
Luke 10:25
And, behold, a certain lawyer stood up, and tempted him, saying, Master, what shall I do to inherit eternal life?
Luke 18:18
And a certain ruler asked him, saying, Good Master, what shall I do to inherit eternal life?
John 3:15
That whosoever believeth in him should not perish, but have eternal life.
John 4:36
And he that reapeth receiveth wages, and gathereth fruit unto life eternal: that both he that soweth and he that reapeth may rejoice together.
John 5:39
Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
John 6:54
Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
Matthew 19:16
And, behold, one came and said unto him, Good Master, what good thing shall I do, that I may have eternal life?
Matthew 25:46
And these shall go away into everlasting punishment: but the righteous into life eternal.
Mark 10:30
But he shall receive an hundredfold now in this time, houses, and brethren, and sisters, and mothers, and children, and lands, with persecutions; and in the world to come eternal life.
Surely for any human with a navel, eternal life means life with a beginning. Are the above examples sufficient?
So how did you miss the above? Does the New World Translation of the Holy Scriptures use different phrasing?
Yes. That translation uses everlasting life in most places, but does include these uses of eternal for events having a beginning or an end:
Jude 1:6
And the angels that did not keep their original position but forsook their own proper dwelling place he has reserved with eternal bonds under
dense darkness for the judgment of the great day.
Habakkuk 3:6
He stood still, that he might shake up the earth. He saw, and
then caused nations to leap. And the eternal mountains got to be smashed.
The commentary in this translation refers repeatedly to humans having eternal life.
Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
I would say here something that was heard from an ecclesiastic of the most eminent degree; ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes.’ Galileo Galilei 1615.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass