a group or cluster of cats.
Origin of clowder
1795–1805; variant of dial. clodder clotted mass, noun use of clodder to clot, coagulate, Middle English clothered, clothred (past participle), variant of clotered; compare obsolete clotter to huddle together; see clutter
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
1811, variant of clutter.
Online Etymology Dictionary, © 2010 Douglas Harper