Sottish means stupid, dull, or very foolish. It describes a person or people whose understanding is thick-headed and lacking in good judgment.
Jeremiah uses the word of children who are wise in doing evil but have no understanding of what is good. The term therefore emphasizes moral and practical foolishness, not merely limited intelligence.
The English word translates a Hebrew term meaning “thick-headed.” The Revised Version expresses the sense as “stupid” or “very foolish.”