A minced oath is a polite, softened version of a swear word or blasphemous phrase, created by altering the sound or spelling to make it less offensive, like saying "gosh" for "God," "darn" for "damn," or "heck" for "hell". These euphemisms allow for the expression of strong emotion without using taboo words, maintaining the original's feel but reducing the shock. 

Key characteristics: 

Euphemistic

Sound-alike: Often similar enough to the original to be recognizable (e.g., "gee whiz" for "Jesus"). 
Examples 

"For Pete's sake!" (instead of "For Christ's sake!"). 

"Zounds!" (from "God's wounds!"). 

"Gadzooks!" (from "God's hooks!"). 

"Crud!" or "Fudge!" (instead of stronger curses). 

Purpose To soften the impact of a curse while still conveying frustration or surprise.