GURU...a dirty 4 letter word?

Advertisers and Marketers have made their own definition for the word guru.

Many use the word guru in their ads and have no clue of the true definition of the word guru.

Now when I see this word I use my own definition.

GURU:

Useless information.

Friend for funds.

Ripped me off.

Use it in sentence:

Look out! don't step in that guru.

What stinks?....did you guru yourself?

My guess on how this word became used in advertising,
a copywriter used the true definition of the word guru for a book
title to describe the author's expertise or great teaching and helping others in the author's field.