I heard U.S. Congressman Bennie Thompson (D-MS) say this yesterday on Fox News Channel.

Problem:
The Congressman used the wrong word for the verb in this popular expression.

Explanation:
The word “error” is a noun and not a verb.

What the Congressman should have used is the word “err”, which looks like “error” but is a verb that means to be mistaken or incorrect.

Perhaps the Congressman simply mispronounced “err” (the verb) as “error” (the noun).

Wondering whether this could be more than a pronunciation problem, I searched Google — with the quotation marks included in the search box — for “error on the side of caution” and “err on the side of caution” and got about 20,200 and 441,000 matches, respectively. That tells me that Web authors have written the expression correctly by a ratio of 21.8:1, which is very good.

Still, over 20,000 matches for “error on the side of caution” indicates a substantial number of confused writers!

Solution:
“We have to err on the side of caution.”