lush

From Middle English lusch (“slack, relaxed, limp, loose”), from Old English *lysċ, lesċ (“slack; limp”), from Proto-West Germanic *laskwī̆, from Proto-Germanic *laskuz, *laskwaz (“weak, false, feeble”), from Proto-Indo-European *lēy- (“to let; leave behind”).

Akin to Old English lysu, lesu (“false, evil, base”), Middle Low German lasch (“slack”), Middle High German er-leswen (“to become weak”), Old Norse lǫskr (“weak, feeble”), Gothic 𐌻𐌰𐍃𐌹𐍅𐍃 (lasiws, “weak, feeble”), Middle Low German las, lasich (“slack, languid, idle”), Low German lusch (“loose”). Doublet of lusk. More at lishey, lazy.

Perhaps a humorous use of the preceding word, or perhaps from Shelta lush (“food and drink”) (the sense "liquor" is older than the sense "drinker"). The Century Dictionary wrote that it was "said to be so called from one Lushington, a once well-known London brewer", but the Online Etymology Dictionary considers lushington (“drinker”) a humorous extension of lush instead.