slosh (n.) Look up slosh at Dictionary.com
1814, "slush, sludge, a watery mess," probably a blend of slush and slop (n.1) in its Middle English sense of "muddy place."
slosh (v.) Look up slosh at Dictionary.com
"to splash about in mud or wet," 1844, from slosh (n.). Meaning "to pour carelessly" is recorded from 1875. Related: Sloshed; sloshing.