What part of "COW" don't you understand?

Last week Abbie made me laugh really hard.

Every morning, when she wakes up, she loves getting on her window stool to look outside. She points at things and names them to me: "twee! (tree)", "kye!(sky)", "ca! (car)!", "sun!", "chichi! (kitty)", and so forth. Well, at one point she excitedly started saying "cow!!! cow!!! cow!!!" and pointing around randomly. So I said: "Abbie, WHERE is the cow? There is no cow there, honey... What cow? Where? Do you mean to say Cow or something else?".

Abbie turned to me, with this look in her eyes that said: "Boy, do you require some patience...! What is wrong with you!" and then, still tapping her index finger on the window, blurted out "MOOOOOOO!!!".

I mean, really. What part of COW did I not understand??