1: to put whiskey into.
2: to combine with whiskey.
3: to infuse with alcohol.
Guest: "No thanks. I have to drive home tonight."
Guy 1: "Dude, I was trying to get with Cathy last night! She's so hot, but she's such a frigid bitch!"
Guy2: "You just have to irish her up first. Then, she'll be like butter in your hand, if you know what I mean."
Son: "Why is Dad crying over that picture of Grandma?"
Mother: "He's all irished up. You know how he gets."