Partial reduplication of כָּתֹם.
כְּתַמְתַּם • (k'tamtám) (feminine כְּתַמְתַּמָּה, masculine plural כְּתַמְתַּמִּים, feminine plural כְּתַמְתַּמּוֹת) [pattern: קְטַלְטַל]