You can have faith in "fidelity," which has existed in English since the 15th century; its etymological path winds back through Middle English and Middle French, eventually arriving at the Latin verb "fidere," meaning "to trust." "Fidere" is also an ancestor of other English words associated with trust or faith, such as "fiduciary" (which means "of, relating to, or involving a confidence or trust" and is often used in the context of a monetary trust) and "confide" (meaning "to trust" or "to show trust by imparting secrets"). Nowadays "fidelity" is often used in reference to recording and broadcast devices, conveying the idea that a broadcast or recording is "faithful" to the live sound or picture that it reproduces.

One of the ways I have heard fidelity or faithful described is "true to the original" or "an exact replica".  This latter description fits with the M-W notes regarding broadcasts or recordings.

What about humans?  Are we "true to the original"?  In one sense, yes.

Our most ancient ancestor, Adam, sinned (Genesis 3:6-7).  While Adam was made in the likeness of G-d (Genesis 1:26, 5:1) Adam's descendants were made in his own (now flawed and sinful) image (Genesis 5:3).  So, too, we have inherited the sin of Adam and, as a result, have inherited death (Romans 5:12).  King David lamented this in Psalm 51:5-

Behold, I was brought forth in iniquity, And in sin my mother conceived me.

Our flesh is true to the original flesh: Adam.

What about our souls?  We are "true to the original" in that sense as well.  In the morning prayers of ancient believers (which are still recited by some today) it is declared "My G-d the soul you placed within me is pure.  You created it, you fashioned it, you breathed it into me.  You safeguard it within me, and eventually you will take it from me and restore it to me in time to come.  As long as the soul is within me I gratefully thank you, O Lord, my G-d and the G-d of my forefathers.  Master of all works, Lord of all souls, blessed are You, O Lord, Who restores souls to dead bodies."

While our biological parents provide our bodies our souls are formed and created by G-d himself.  While we cannot (of our own accord) keep our soul free from sin, we can trust in Him who created our soul to redeem it (Psalm 49:15, Psalm 55:18, Psalm 69:18) so that we can walk in His ways.

To Him be the glory forever.  Amen.