I got this nugget of information off the tomcat-user list this morning.
I talked to the original Tomcat author, James Duncan Davidson, about the name choice. He gave me a surprising answer. Here's a bit of history... Tomcat was born in response to the need for an independant servlet specification implementation. James wrote it hoping that it would eventually be open sourced. He figured that since most open source projects had O'reilly books about them that he should name it after an animal. Essentially he was thinking of an animal that would go on the cover of an O'reilly book. He came up with "Tomcat" since the animal represented something that could take care of itself and fend for itself. That's how he came up with the name.
And Craig McClanahan tells us why he named the Catalina Engine so:
Using "Catalina" was my idea, because I wrote most of the original code that became it. The reasons are mundane, but here they are for the record: * Even though I don't live in Southern CA, I've always liked what I've read and seen of Catalina Island. * One of the towns on the island is Avalon, and we were (at the beginning) considering using the Avalon Framework (http://jakarta.apache.org/avalon/) for the internal architecture. It would have been a cute tie-in, but alas it didn't happen that way. * When I'm coding, I regularly have one or more cats wandering around my lap and adding to the whitespace when they don't think I put enough (you don't need fingers to press the space bar :-). Another "code name" you'll hear in the Tomcat world is Jasper -- that's the name of the JSP page compiler part of Tomcat. That name was carried over from even before my time, but I'm sure it probabbly came from the alliteration (JaSPer).