ESL Madness

Why is it that the English language calls groups of things different names? What a nightmare for an English learner. Anyone else remember having to memorize the madness when you were in school?

What do you call a group of

cattle - herd
fish - school
geese - gaggle
whales - pod
dogs - pack
birds - flock
sheep - flock

and so on.

Anyone know what you call a group of cats?
Check out this link.