An Etymological Dictionary of the German Language/Annotated/Schmerl
Schmerl, masculine, Schmerlin, ‘merlin,’ from Middle High German smirl, masculine, smirlîn, ‘mountain falcon,’ Old High German smirl, masculine, Old Icelandic smyrell; loan-words from Ron.; compare Italian smerlo, smeriglione, French émerillon, ‘stone-falcon’; English merlin comes from French. The Romance name of the bird is usually derived from Latin merula, ‘blackbird’; “it is said that the Latin word is applied to a bird similar to the blackbird.”