My wife heard this yesterday.

Problem:
“Disconcerning” is a nonsense word.

Explanation:
Nearly everyone who says “disconcerning” actually is trying to say an adjective whose meaning is causing an emotional disturbance.

“Disconcerting” (notice the ‘t’ before the ‘ing’) — not “disconcerning” — is the adjectival form of the verb “disconcert”.

I believe that the use of “disconcerning” is consistent with my “Devolution toward Simpler” linguistic hypothesis. It’s simpler to say “disconcerning” than to say “disconcerting” (which requires the speaker to emphasize the ‘t’).

For fun, I searched Google for each of the following words and got about the indicated numbers of matches:

• disconcerning — 22,600 matches
• disconcerting — 2,260,000 matches

This tells me that Web authors have written the word correctly vs. incorrectly by a ratio of 100:1, which is very encouraging.

Solution:
“Disconcerting”