by design

On purpose, deliberately, as in Whether by luck or by design, his application was accepted. This term, originally put as on design, uses design in the sense of “plan.” [First half of 1600s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.