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I understand from your post that when typing the word "it" it is replace with "I.T." Check to see if at some point it was added as a text replacement under Settings > General > Keyboard > Text Replacement. If so, slide the text replacement entry to the left and tap delete. The following article has some additional information about Text Replacement:
How to use Auto-Correction and predictive text on your iPhone, iPad, or iPod touch - Apple Support
Best Regards.Set up text replacement
With text replacement, you can use shortcuts to replace longer phrases. When you enter the shortcut in a text field, the phrase automatically replaces it. For example, you could type "GM" and "Good morning" would automatically replace it.
To manage text replacement, tap Settings > General > Keyboard > Text Replacement.