While the focus spelling here is MURDUCK, records and compilations are continually being created with some variation on the theme.
Below are just a few of the spelling varieties (variations, in some circles, deviants in others) which I have encountered concerning people who should rightfully have been identified as MURDUCK:
Murdoch, and Murdock, of course.
But also: Mardeck, Mardick, Mardicks, Mardock, Mardocks, Mardok, Marduck, Martek, Merdick, Merdicks, Merdock, Merdocks, Merduck, Meurdock, Middick, Midduck, Moerdyk, Moordack, Moordick, Moordock, Moorduck, Mordah, Mordeck, Mordick, Mordicke, Mordicks, Mordock, Mordocke, Mordocks, Morduck, Moredeck, Moredick, Moredock, Moreduck, Morodeck, Morodick, Morodock, Mortock, Morttocks, Muddicks, Muddock, Muddocks, Muddox, Mudick, Mudicks, Murdach, Murdack, Murdah, Murdaugh, Murdauk, Murdeck, Murdick, Murdicks, Murdochs, Murdocks, Murdocq, Murdoff, Murdok, Murdox, Murducke, Murtagh, Murtaugh, Murtock, Murtogh, Muttock, Muttocks, Muttox, Muttuck, Muttucks, Muttukes, Muttux.
Many of these variant spellings have been applied to my surname in my lifetime!