make one's head spin
Cause one to be giddy, dazed, or confused, as in The figures in this tax return make my head spin. This phrase employs spin in the sense of “rapidly gyrating,” a usage applied to the brain or head since about 1800.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.