Catach [ass] [covering]
Castach is originated form an army term or more like it an initials of an army term called "Lechsot et Hatachat" which means covering your ass.
For example in many cases especially in voluntary armies a sergeant / commander doing things in order to say "I followed Procedure" that act is called "Castach" which is as mentioned "Covering Ass".
Catachism
What a tomcat who can’t spell calls the stuff he exudes when sufficiently sexually stimulated by a particularly cute pussy.
Tweetybird had to perch quietly while Sylvester moaned, groaned and ultimately climaxed in a spray of catachism he directed at least at the correct end of the pussy presented to him.