Sharp as a tack

Meaning

Mentally quick or clever.

Usage

Often used to compliment someone's intellect.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Tacks were sharp nails; the phrase praises keenness.

Mid-1800s American slang for quick-witted folks.