tight as a tick - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Drunk, as in She was tight as a tick after just one glass of wine. This expression alludes to a tick engorged with the blood of the animals it feeds on. [Slang; mid-1800s]