When you are surrounded by Arabic people and in order to ensure you are saying the truth they tell you to "say wallah"
Mark: "That hot girl Trixie was all over me last night"
Ahmed: "Really? Say wallah"
Mark: "Wallah man, I swear"
Ahmed: "Really? Say wallah"
Mark: "Wallah man, I swear"
by Leanasaur January 03, 2010