It would appear that someone has played a practical joke on you by creating a malicious entry to your autocorrect entries. Click File, then Options.

With the Word Options open, select Proofing from the list on the left and then click the AutoCorrect Options button in the upper right.

In the AutoCorrect dialog, scroll through the list in the lower half of the AutoCorrect tab. Select any entries you find unwarranted or malicious and click the Delete button.

Remember to click OK, then OK on the way out.