[Help-bash] What does kqueue means?

[Jorge]

I'm trying to understand what the word kqueue means to understand the 
option -k from ulimit, which says:

> The maximum number of kqueues that may be allocate

Someone told me that it's a BSD thing via #bash IRC, but I have no idea 
how to find more info about that. man sigqueue nor man setrlimit didn't 
help me find it out.