suds (n.) Look up suds at
1540s, "dregs, leavings, muck," especially in East Anglia, "ooze left by flood" (according to OED this may be the original sense), perhaps borrowed from Middle Dutch sudse "marsh, bog," or related words in Frisian and Low German, cognate with Old English soden "boiled," from Proto-Germanic *suth-, from PIE *seut- "to seethe, boil" (see seethe). Meaning "soapy water" dates from 1580s; slang meaning "beer" first attested 1904. Related: Sudsy.