"Gill" as in "giving a gill" A term used around the late 80s-early 90s, possibly regional, by children as a proclamation that someone/a friend just said something incredibly stupid or incorrect, AND that they deserve to be humiliated. It was shouted as he/she simultaneously burns the back of the other person's neck with a fast horizontal rub of the hand. Similar in nature to an Indian burn.
Person 1: Yeah, well your mother is your father. (I'm paraphrasing.)
Person 2: Not funny. You deserve a gill for that. Gill!
Person 1: Ow. What the hell?
Person 3: You're 17 and still giving people gills?
Person 2: Oh, wow. I haven't remembered a gill in a long time. Hah.