From the scholia to Sophocles, Ajax 297 (web address 1), where the accusative plural headword occurs, properly, as a two-word phrase. The point of the comment, nevertheless, is not that the phrase should be written as a single compound word; instead, the commenter is concerned that someone might think that Ajax kills not herdsman-dogs (ku/nas both=ras) but both dogs, ku/nas, and herdsmen, both=ras.
cf. generally beta 405.