kibble (n.)

"ground-up meat used as dog food, etc.," 1957, apparently from the verb meaning "to bruise or grind coarsely," which is attested from 1790, first in milling; a word of unknown origin. The same or an identical word was used in the coal trade in the late 19c. and in mining from the 1670s for "bucket used to haul up ore or waste."