The headword noun does not appear in this form, the genitive singular, in extant literature. However, it does occur in the scholia vetera to Homer, Iliad 13.171 ("Imbrius, the son of Mentor, rich in horses"), where it is a fanciful variant of Mentor: "And 'of Mentor' should have been 'of Kentor' [of a goader]: for someone rich in horses will be used to goading."
For the nominative plural ke/ntores see Homer, Iliad 4.391, 5.102, and in epigrams.