They started as same word, but their meanings have drifted apart over time.
Editor Emily Brewster clarifies the difference.
Comedian ISMO on what separates a boot from a trunk
We believe the popular usage of this word is correct
'Poets laureate'? 'Court-martials'? The curious history of postpositive adjectives in English.
How 'literally' can mean "figuratively"
Some imitative words are more surprising than others
