in that - 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.
For the reason that, because, as in In that you will be busy for the next few weeks, let's go over your paper now. [Mid-1400s]