Also, seeing as or seeing as how. In view of, inasmuch as. For example, Seeing that you're coming anyhow, I decided not to take notes for you, or Seeing as they liked her first book, they were sure to make a good offer for the second one. The first expression was used by Shakespeare in Julius Caesar (2:2): “Seeing that death, a necessary end, will come when it will come.“ The variants are colloquialisms and are recorded from the second half of the 1900s, although they probably have been in much longer use orally.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.