How do I delete words from autocorrect?

Since the update to Marshmallow, and now especially with the keyboard update, I am having words autocorrect that are not part of any dictionary that I have.

I have deleted every word in the personal dictionary

I have cleared the "learned words" in the keyboard

But still, whenever I type tv (as in TELEVISION), the keyboard autocorrects it to TTV

As I work in the broadcast industry, I type TV a lot. This is beyond annoying. How do I fix it - and a factory reset might well have it pop back in because it's obviously saved SOMEWHERE!!!

Any assistance appreciated!

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