late 13c. as a form of address, 1570s as a synonym for "loved one;" from sweet (adj.) + heart (n.). As an adjective, with reference to labor contracts, it is attested from 1959.
实用例句
1. "Daddy! I came second in history" — "Well done, sweetheart!"
“爸爸！我的历史得了第二名。”——“考得好，亲爱的！”
来自柯林斯例句
2. "I want to go with you, Daddy."—"Now, now, sweetheart."
“爸爸，我想和你一起去。”——“好吧，好吧，小宝贝。”
来自柯林斯例句
3. Happy birthday, sweetheart.
生日快乐，亲爱的。
来自柯林斯例句
4. I married Shurla, my childhood sweetheart, in Liverpool.