I am fascinated by this word!
Jonah 2:8 in the Orthodox Jewish Bible (OJB) reads “They that observe lying vanities forsake their own chesed.”
Definition of chesed/hesed—There were actually several different definitions for this Hebrew word, the most common of which was loving-kindness.
This explanation, a bit more than a definition was found at https://discovertheword.org/2010/09/08/the-old-testament-word-hesed-and-the-profound-meaning-it-has-for-us-today/
Hesed is difficult to translate because it stands for a cluster of ideas—love, mercy, grace, kindness. It wraps up in itself all the positive attributes of God. Hesed is one of the Lord’s most treasured characteristics.
Hesed is a quality that moves someone to act for the benefit of someone else without considering “what’s in it for me?”
It may be translated as “loyal love.” Sometimes the emphasis is on “loyal” and other times the emphasis is on “love.”
Look at some other translations of Jonah 2:8
21st Century King James Version (KJ21) “They that observe lying vanities forsake their own mercy,”
American Standard Version (ASV) “They that regard lying vanities
Forsake their own mercy.”
The only difference between these two translations is observe versus regard.
What does vanity mean in this context? 
This is the image that first comes to my mind when I hear the word vanity. Insert picture.
Next is the quality of being vain or taking too much pride in oneself.
Then I was surprised that it can mean what at first glance appears almost the opposite—the quality of being worthless or futile.
All 3 of these, on overthinking, can mean the same thing. Look at that huge mirror on the vanity I chose for this blog. And are not the drawers used to store makeup and jewelry, things designed to make one take more price in her appearance? And is it not true that often the outer appearance does not reflect the true nature of one’s heart/soul?
Setting aside the above overthinking paragraph, it seems like the 3rd definition is the one which most accurately reflects what is being described in Jonah 2:8. Not just a worthlessly futile thing but a lying worthlessly futile thing.
Going on to a couple other translations:
Christian Standard Bible (CSB) “Those who cherish worthless idols abandon their faithful love,”
Amplified (AMP) “Those who regard and follow worthless idols turn away from their [living source of] mercy and lovingkindness.”
So this worthlessly futile thing is an idol!
We follow the vanities/idols of our unfaithful hearts, be they any of the mind-numbing activities we use to . . . wow! . . . numb our minds! These could be addictive behaviors, unrighteous anger, self, maybe even things that aren’t necessarily bad but become bad when used the wrong way. In so doing we are actually repenting—or turning away from—the chesed/hesed (It wraps up in itself all the positive attributes of God. Hesed is one of the Lord’s most treasured characteristics) Abba so freely gives.
Please join me as, with the help of my Father, I learn to repent of the lying vanities and embrace the chesed.
My Father in Heaven, I come before you having followed the lying vanities a large part of this day.
Tomorrow is a new day, and according to Lamentations 3:22-23 because of your great love (hesed/chesed) your compassions and mercies are new every day. I receive your perfect compassions and mercies working in my soul tomorrow, knowing that your love is making me complete.
Now, because of you, Lord, I will like down in peace and sleep comes at once, for no matter what happens, I will live unafraid!
JLM in Euroclydon 