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.
merry widow
merry-andrew
merry-go-round
merrymaking
merrythought
Mersey
mesa
mesalliance
mescal
mescaline
mesdames