type of fish with a head formed to attach to objects or other fish," 1560s, from Latin remora "sucking fish," literally "delay, hindrance," from re- "back" (see re-) + mora "delay" (see moratorium); so called because the fish were believed by the ancients to have the power to retard a vessel to which they attached themselves.
Hence, in 17c.-18c., "an obstacle, an impediment" (the first sense of the word in Johnson's dictionary). The belief predates the Romans: in Greek, they were ekheneis, from ekhein "to hold" + naus (dative nei) "ship." Pliny writes that Antony's galley was delayed by one at Actium. Sometimes called in English stayship or stopship.