English river running past Liverpool, c. 1000, Mærse, probably "boundary river," from Old English mæres (genitive singular of mære "boundary, object indicating a boundary;" see mere (n.2)) + ea "river." Related: Merseysider. Mersey beat, in reference to the popular music style associated with the Beatles, is by 1963.
Entries linking to mersey
mere n.2
"boundary line" (between kingdoms, estates, fields, etc.), now surviving in provincial use or place names, but once an important word, from Old English mære "boundary, object indicating a boundary," from Proto-Germanic *mairjo- (source also of Middle Dutch mere "boundary mark, stake," Old Norse -mæri "boundary, border-land"), related to Latin murus "wall" (see mural (n.)).
Hence merestone "stone serving as a landmark" (Old English mærstan); mere-stake "pole or tree standing as a mark or boundary" (1620s); meresman "man appointed to find boundaries" (of a parish, etc.). In Middle English meres of erthe (c. 1400) was "the ends of the earth."
ea n.
the usual Old English word for "river, running water" (still in use in Lancashire, according to OED), from Proto-Germanic *ahwo- (source also of Old Frisian a,Old Saxon aha,Old High German aha,German ahe-,Old Dutch aha,Old Norse "water"), from PIE root *ekweh- "water" (see aqua-). "The standard word in place-names for river denoting a watercourse of greater size than a broc or a burna" [Cambridge Dictionary of English Place-Names].