I didn't know the etymology of
Arlo until I clicked on it just now. Neat!
I like
Arlo because of Mr. Guthrie. It's gutsy and fun. Of your combinaitons I like / love:
Arlo DavidArlo FrancisArlo Frederick (!)
Arlo PhilipArlo ConstantineArlo WilliamArlo Hannibal (!)
I want to love
Arlo Thomas, but I can't get Marlo
Thomas ("That Girl") out of my head. But the newest generation won't have a clue who that is so I wouldn't worry about it.
And how do the Irish get three meanings (between two mills) out of two syllables? No need to answer. It's just something fun to ponder.