Oh cool!  Did you know owls are nocturnal?  That's where the term night owl is derived from.
Interestingly, the term night owl refers to the primary nocturnal habits of the owl! haha
I am a night owl, I can't seem to make myself go to sleep early, I always end up staying up really long. Oh I see!   Did you know the night owl's opposite is a lark, or early bird?  They go to sleep at a time considered early, and wake early. I understand, it' hard to wake up early during the day. Ah yes.  Oh by the way, in Scandinavia they call early birds "A-people," while they call night owls "B-people!" I never heard of it, I kind of like early bird and night owl phrases more to be honest. I've always wanted to visit Scandinavia.
The term is derived from the primarily nocturnal habits of the owl.