Means: Something hilarious
Usage: "Have you seen Charlotte's latest outfit? Tres hollage!"
Posher teens have their own version of Yoofspeak, their own mix of would-be street slang, babytalk and invented expressions, typically in the form of girly yells of approval (by both sexes) and squeals of delight (ditto).
When the denizens of the middle-class playground are trading witticisms, a favourite trick is to insert touches of French - the odd real word ("quelle disaster", "beaucoup trouble") and Franglais pronunciations. "Rummage" (sex) and "bummage" (enthusiasm) have been frenchified, but the current favourite is "hollage", meaning huge amusement or hugely amusing, pronounced to rhyme with English "college" or like French "collage", or, some young purists insist, as three-syllable "holla-age".
It looks as if the little sophisticates have adapted "holla" (the hip-hop version of "holler", meaning to yell), one of cool Yoof's iconic expressions from the Noughties, and slightly misunderstood it in the process, since it originally described phoning, praising or seducing rather than braying with laughter.