A secret plan or undertaking, as in I think there's something in the wind for Mom and Dad's anniversary. This expression alludes to the carrying of a scent by the wind. [First half of 1500s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.