Clowder

As a noun this term can be used as the distinctive group phraseology for a number of cats.

Example: With luck, my kindle of kittens will grow up to be a fine clowder.

Checked against my copy of The Quickaway Crossword Dictionary, compiled by H. W. Hill and published by Morrison & Gibb Ltd. Although undated, it would appear to have ben published during the period 1955-1957