blabbermouth / noun

blab·​ber·​mouth ˈbla-bər-ˌmau̇th 
a person who talks too much especially:  TATTLETALE
Everyone knows one.  There’s the one that occupies conversation at the dinner table to the point that no one can hear you ask for the salt.  There’s the one that sits behind you in the theater and determines the outcome ten minutes after the movie starts and is invariably wrong. And not just the movie theaters.  I once had to reprimand a woman at a Broadway musical who insisted on singing along.
Excuse me m’am but I paid good money to hear Patti Lupone, not you.
A person on the subway that talks so loud that when the conductor announces the train is out of service, you don’t hear it and end up in Coney Island.  Or how about this zinger of a lead-in:  
You have to swear you won’t tell this to anyone but … 
What if you honestly could care less about the topic and don’t want to hear what it is that you’ll now have to hold secret?  The pressure’s unduly passed onto you.  Just how large an ego does one possess to think their opinions, observations and gossip supersede everyone else’s? There’s also the one that has to outdo you.
Me:      I broke my elbow and the pain is unbearable.
Them:  Oh you don’t know pain.  Fall down a flight of cement stairs and get back to me.
Me:      Umm I probably won’t.
Them:  Damn right you won’t.
So does ego drive the blabbermouth?  I get that some blabber is driven by loneliness.  I’m somewhat sympathetic to that as I’m sure I’ve blabbered a few times, usually with wine involved. But the typical blabbermouth is just far too enamored with themself that they feel obligated to share anything with everyone.  That they can enrich people’s lives by sharing a modicum of their wisdom.  Parents blabber to their kids … well at least mine did.  According to them I did not and would not appreciate things until I suffered like they did, and what they considered to be suffering didn’t involve starvation or neglect.  More like I can’t believe they don’t have my size in navy blue.  That sort of suffering.  Having to decide between black and brown as an alternative.  
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A real Sophie’s Choice.  I first heard the term blabbermouth on The Honeymooners. Ralph Kramden used to bellow about what a blabbermouth his mother in law was when in fact he was just as much a blabbermouth as she was and he resented her stealing his air time.  Kind of like someone residing in the White House.  Now that’s a blabbermouth. And blabbermouths tend to dismiss the truth in favor of anything adding legitimacy to the subject they’re blabbing about. That’s a serial blabbermouth.  They extend zero respect to the intellect of their victim thinking they’ll just believe anything they say because they say it loudest and never allow a conversation to evolve. Is that called preaching to the choir or preaching from the pulpit?  I don’t know.  As I’ve said before, I only went to church when my high range soprano mother landed a solo with the choir. She was most obsessed with center stage on Christmas Eve.
Her:  Well how was I?
Me:   Great.
Her:  Just great?  What did the others around you say?
                                                                                                                                                                        I wish someone had said You have to swear you won’t tell this to anyone but …