Today’s letter is O and the associated topic is -ologies and -isms.
I love words and etymology. As a child I used to read the dictionary recreationally, and even asked for a chunky dictionary for my birthday one year, The Chambers Dictionary.
Many years later (after I'd finished University) I discovered another dictionary-type book titled Ologies and Isms and its this book that I'm writing about.
Despite the title, it's not just limited to words containing those two suffixes. It does explain the etymology for many words and phrases which are used in English.
If etymology is your thing you'll probably enjoy it. Also of possible interest is Etymonline which I occasionally use too.