In Tremper Longman's commentary on Proverbs, he translates Prov. 9:4b this way: "she says to those who lack heart." The bolded phrase is a rendering of חֲסַר־לֵב (chasar-lēb). It is very literal, and literally accurate — could be "lacking heart" or "short on heart."
You'll see that all versions get a little dynamic here, ranging from "him who lacks sense" (so essentially ESV, CSB, NIV, RSV, NRSV, etc.), to "him who lacks understanding" (so essentially NAS, NET, ASV, KJV, NKJV), to "those who lack good judgment" (NLT).
So what does "heart" mean? Here's what I said in God's Wisdom in Proverbs:
Contrary to years of Christian traditional definition, the heart is not primarily the seat of the emotions, but rather of intellect, volition, and evaluation. It is used specifically of memory in various places, including Deuteronomy 4:39 and Proverbs 4:21.
Wouldn’t “brain” be the better modern term for this idea? Why is the heart used for the mind, rather than “brain”? As a matter of fact, the word “brain,” as a part of the body, is never mentioned in the OT. The word simply was not in use in the Hebrew working vocabulary as it is in modern English. The question is not, “Why didn’t the Hebrews use our word,” but rather, “What Hebrew word (if any) has a meaning equivalent to ‘brain’?”—and usage shows that the answer is, “Heart.”So why not translate it literally, as Longman does? Because "lacking heart" is a familiar English expression with an established meaning. When we say someone "lacks heart," we aren't saying that he is deficient when it comes to God-fearing wisdom, as Solomon means. We mean that he lacks courage, he lacks fortitude, he lacks spirit — none of which is Solomon's sense.
[Phillips, D. (2011). God’s Wisdom in Proverbs: Hearing God’s Voice in Scripture (p. 115). Woodlands, TX: Kress Biblical Resources.]
So there we have to opt either for something a bit dynamic, as above, or do what I do: "short on brains," with a footnote like "Literally 'lacking of heart.'"
Because in this case, the literally literal is literally misleading.