“Red herring” began as a name for a strongly cured fish, then became a metaphor for a distraction that pulls attention away.

“Home in” is the older phrase for moving toward a target or narrowing focus. “Hone in” came later and is now widely used.

Earlier English had no fixed spelling, so through appeared in many forms. Printing and dictionaries gradually helped standardize it.

“Keep your powder dry” began as literal military advice. Today it means staying prepared, especially for risk, trouble, or sudden action.