You know how some people get on Wikipedia and follow hyperlinks for hours? I was doing that in grade school. With real encyclopedias. By the time dinner rolled around, I'd have half the set spread out on the family room floor.
We never owned any encyclopedias, just various dictionaries. But I have a sneaking suspicion that if we did, I'd have done the same thing you did, Oniya.
I also think that in my case, being French-Canadian, and bilingual to boot, I got away with more words than I expected. Cuz a lot of those later words were French, and I know the definition of them in both languages. If I wasn't French and English, I likely would never have known, say... Portmanteau.