Heck is a euphemism for hell. It was first used in the late 1800s. It was never associated with fuck.
At all.
Ever.
The only time heck and fuck will be mixed is when I say, “Why the fuckin’ heck would you believe this?”
The leading theory is that it derived from the Scottish word “hech” which meant “surprise or shock.” Like if a sheep bites you.
“Oh hech! That hurt, ya bloody sheep. I just wanted to cuddle!”

