common Irish surname, Gaelic Murchadh "sea-warrior." The Celtic "sea" element is also in names Muriel (q.v.), Murdoch (Old Irish Muireadhach, Old Welsh Mordoc "mariner"), etc. As colloquial for "a potato" by 1811, apparently in allusion ot it being a staple food of the Irish.
Murphy bed (1912; in full Murphy In-A-Dor Bed) is named for U.S. inventor William Lawrence Murphy (1876-1959). By happy coincidence, Murphy was an illiterate 18c.-19c. perversion of Morpheus, god of sleep. Murphy's law (1958) is used of various pessimistic aphorisms (often reducible to "if something can go wrong, or be misunderstood, it will"). If there ever was a real Murphy his identity is lost to history. Said to be military originally, and it probably pre-dates the earliest printed example (the 1958 citation calls it "an old military maxim").