Need an origin story for a classic Full House catchphrase? Well, you got it, dude!

While being honored during last weekend's taping of the TV Land Icon Awards, John Stamos revealed that his classic recurring line, "Have mercy," was all thanks to Happy Days creator and fellow Legend award winner, Garry Marshall.

"He always said, ‘Get a catchphrase, you need a catchphrase.' I'm not kidding you," Stamos explained during his acceptance speech. "The 'have mercy' thing came out of, 'Oh s**t, Garry told me I had to have a catchphrase."

EXCLUSIVE: Jodie Sweetin Has High Praise for John Stamos' New Girlfriend

Well, apparently we have more to thank Marshall for than we knew!

Meanwhile, there's more mercy to be had, as Stamos has been seen out and about lately with his new girlfriend, model and actress Caitlin McHugh.

WATCH: John Stamos and New Girlfriend Caitlin McHugh Step Out for PDA-Filled Ice Cream Date

The actor's Full House and Fuller House co-star, Jodie Sweetin, gushed to ET in March about McHugh.

"I actually met her a couple days ago. She is delightful," Sweetin said. "She's really sweet and we are welcoming her into the family. They're adorable, and we really like her."

WATCH: John Stamos Shares Home Video of Adorable Olsen Twins on 'Full House' Set in 1989

Watch below for more:

TV Land's Icon Awards, hosted by George Lopez, will air Sunday, April 17, at 9 p.m. ET.