Easton’s Bible Dictionary
Lees: (Heb. shemarim), from a word meaning to keep or preserve. It was applied to "lees" from the custom of allowing wine to stand on the lees that it might thereby be better preserved (Isaiah 25:6). "Men settled on their lees" (Zephaniah 1:12) are men "hardened or crusted." The image is derived from the crust formed at the bottom of wines long left undisturbed (Jeremiah 48:11). The effect of wealthy undisturbed ease on the ungodly is hardening. They become stupidly secure (comp. Psalm 55:19; Amos 6:1). To drink the lees (Psalm 75:8) denotes severe suffering.