A phrase popularized in the 1980s by U.S. teenage females who were viewers of the American sitcom "Full House." For some yet unknown reason, these persons found the show entertaining and desired to emulate actress Candance Cameron whose character repeated the phrase incessantly on the show.
The phrase then spread like a virus, infecting the vernacular of people of older and younger generations regardless of gender...these people were born without the ability to discern that this phrase was, to put it in the parlance of our current times, "fucking stupid."
Is used to express approval or liking.
Person A: "Hey, its TGIF on ABC tonight! Wanna watch 'Full House?'"
Person B: "Cool beans!"