The effect is an extremely runny nose (Pm).
References from the canon
- Ron threatened to learn this curse, then use it on Hermione and Neville if they all got caught roaming the school at night on their way to a duel with Draco Malfoy (PS9)
"bogy" uncertain origin: "Old Bogey" = The Devil c. 1836; "bogle" Scottish phantom or goblin c. 1505 and "bogge" terror, possibly from "bwg" Welsh ghost and "bwgwl" fear Yeah, maybe. But more likely: "bogey" British slang: booger