Slop
mid 16th century (in the sense ‘to spill, splash’): probably related to slip3. Early use of the noun denoted ‘slushy mud’, the first of the current senses (‘unappetizing food’) dating from the mid 17th century.
wiktionary
From Middle English slop, sloppe, slope, from Old English *slop (found in oferslop(“an outergarment, surplice”)). Cognate with Icelandic sloppur(“a long, loose gown”).
Probably from Middle English *sloppe (attested in plural form sloppes), representing Old English *sloppe (attested in cū-sloppe), related to slip.
Alteration of ecilop, from back slang for police.
etymonline
slop (n.)
c. 1400, "mudhole," probably from Old English -sloppe "dung" (in plant name cusloppe, literally "cow dung"), related to slyppe "slime" (from PIE root *sleubh- "to slide, slip"). Meaning "semi-liquid food" first recorded 1650s; that of "refuse liquid of any kind, household liquid waste" (usually slops) is from 1815. Meaning "affected or sentimental material" is from 1866.
slop (v.)
"to spill carelessly" (transitive), 1550s, from slop (n.1). Intransitive sense from 1746. Related: Slopped; slopping.
slop (n.2)
late 14c., "loose outer garment," perhaps from Old English oferslop "surplice," which seems to be related to Middle Dutch slop, Old Norse sloppr (either of which also might be the source of the Middle English word), perhaps all from Proto-Germanic *slup-, from PIE root *sleubh- "to slide, slip" on the notion of a garment one "slips" on or into (compare sleeve). Sense extended generally to "clothing, ready-made clothing" (1660s), usually in plural slops. Hence, also, slop-shop "shop where ready-made clothes are sold" (1723).
