“Bless your heart” can have several meanings in the South, and it’s not always a disguised way of saying “stupid”, although it can be. Examples of use of the phrase “bless your heart”.
Examples as a gentle, socially polite putdown- “Bless your heart” can be said to someone who is just not catching on to something that’s very obvious to everyone else, like if everyone in the car is able to buckle their seat belts except cousin Brenda Sue who somehow is trying to hook her waist belt buckle to the car seat belt fastener, then someone would say “Why bless your heart, Brenda Sue, just let me show you how to fasten your seat belt”, but what everyone is really thinking but not saying is “Brenda Sue, you’re acting like you don’t have a brain in your head”, much kinder to say “Bless your heart, Brenda Sue”. OR Billy Joe’s teacher asks him in front of his mother how old he is and he says “I am 5 years old and he only holds up 3 fingers” and then his teacher gently, but with strong concern asks him one more time again how old he is and he says “I am 6 years old and he holds up 10 fingers”. At this point, Billy Joe’s teacher looks at both Billy Joe and his mother and says “Billy Joe, bless your heart and bless your mamma’s heart too”. But Billy Joe’s teacher is really thinking but not saying “Poor Billy Joe probably couldn’t find his way out of a small wood shed with directional arrows lit up and pointing to the open door”.
Example as a sincere phrase of concern to a friend who’s having a rough day. Jackie Rattles just found out that her auto insurance has increased $5 a month. Down South, we’d say “Jackie, that’s a crying shame. God bless your heart”. Note, sometimes the word “God” is inserted to make the phrase “bless your heart” may sincere sounding.
Example as a term of happiness and congratulations to someone who has achieved something great. Judy Rivers just found out that she finally achieved her weight loss goal and she can easily fit into her blue jeans, down South her friends would tell her “Bless your heart, that’s fantastic news!”
In addition, “bless your heart” can be used in several different alternate ways. Down South, you might hear someone say “Bless your poor little old heart”, or “Bless your cotton picking heart”, or “God bless your sweet heart”.
And that, Julie, is what “bless your heart” can mean in three examples. God bless.
My own personal experience.