merlin (n.)

small, strong European species of falcon, late 14c., merlioun (perhaps early 14c.), from Anglo-French merilun, a shortened form of Old French esmerillon "merlin, small hawk" (12c., Modern French émerillon), from Frankish *smiril or some other Germanic source (compare Old High German smerlo, German Schmerl "merlin"). Spanish esmerejon, Italian smeriglio also are Germanic loan-words. OED rejects connection with Latin merula "blackbird."

name of the sorcerer and soothsayer in Arthurian legends, from Old French form of Welsh Myrddhin, probably from Old Celtic *Mori-dunon, literally "of the sea-hill," from *mori "sea" (from PIE root *mori- "body of water") + dunom "hill" (see dune).