Grandpa got on the grandson's case (6 years old) because he wore his baseball cap in the house. He really nagged (bad manners in and of itself). But, the little guy asked me what the rule was and who made it up and why? Having gramps say "because I said so" didn't quite cut it.
How do I research it? I came up with some ideas that made sense, like in the olden days men wore hats to protect their heads while working in the fields (as in that is how yarmulkes got their start, I believe) and had to remove them because they were sweat-soaked and dirty. Also, it is matter of trust, with a hat on you cannot see the eyes.
We are all interested in this
Dear We are all interested in this,
One source often referenced about how hat etiquette originated is Emily Post.
From Emily Post's Best Question Archive For the week of February 9, 2004 (www.emilypost.com):
"Hat traditions and manners may have originated in medieval times when knights lifted their face guard to show who they were, or in the days of the cowboys when a hat was lifted and removed to show there was no weapon hidden underneath. It became a sign of respect to others that has always remained."
American Heritage New Dictionary of Cultural Literacy (www.bartleby.com) defines yarmulke:
"In Orthodox Judaism and Conservative Judaism, a skullcap worn by men as a sign of reverence while praying to God or talking about him."