I heard a Fox television sports commentator say this last evening during Super Bowl XLII.

Problem:
This phrase does not contain the correct adjective for the euphemism.

Explanation:
“Unchartered territory” would refer to territory that has not been chartered.

The definition of the adjective “chartered” is related to an arrangement of leased, exclusive, temporary transportation for a group of travelers.

Given that one charters transportation, not territory, “unchartered territory” makes no sense.

In contrast, given that one can map — or chart — territory, the correct adjective for the euphemism is “uncharted”. That is, “uncharted territory” is the euphemism that was mangled by the sports commentator.

For fun, I searched Google — with the quotation marks included in the search box — for “unchartered territory” and “uncharted territory” and got about 59,600 and 734,000 matches, respectively. That tells me that Web authors have written the euphemism correctly by a ratio of 12.3:1, which is good, but not excellent.

I believe that the spoken use of “unchartered” instead of “uncharted” in the euphemism is consistent with my “Devolution toward Simpler” hypothesis. It is simpler to pronounce the “ered” sound than to pronounce the “ed” sound.

Solution:
“Uncharted territory”