One who crays, or a person who catches crayfish; alternatively, one who cries or complains (from 'craye' meaning to cry).
From 'craye/cray' + '-er' (agent suffix indicating one who performs the action). Could derive from either crayfish-catching or from an archaic sense of 'craye' meaning to cry.
Agent nouns with '-er' are endlessly productive—'baker,' 'maker,' 'crayer'—medieval English speakers could turn almost any verb into a job title!
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