From Toby Gottfried:
Apropos your comments about “threes,” it may be hard to find, but I have a book from my college days which talks about this. It’s an anthropology anthology (that’s not a typo) from 1968 called Every Man His Way, edited by Alan Dundes. Starting on p 401 is an essay by Prof Dundes called “The Number Three in American Culture” which discusses its pervasiveness in depth.
learn your A B C ‘s
NBC/ABC/CBS (Three networks, three letters each)
Auto Industry: The Big Three (well, for a long time)
Third Party Candidates
Baseball: three strikes, three bases, three outfielders
His list of references is stretched over . . . three pages.
Yada, yada, yada . . . blah, blah, blah.
(Actually: Thank you, thank you, thank you.)