Take careful aim, as in The debater drew a bead on his opponent. This term, dating from about 1830, alludes to the bead on a revolver or rifle, that is, a small knob in the foresight. [c. 1930]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.