Traditionally when creating SharePoint (or SharePoint Online) list columns, you would first navigate to the Settings page for the List you wanted to add a column. Then you would click “Create column” under the list of existing Columns. This will create the column and the internal name will be a double encoded (click link, scroll down) version of what you typed. You can check this by clicking on the column name after creation and viewing the URL. (See Image Below)
In SharePoint Online and SharePoint 2013 on-prem, there is another option for adding columns to a list: Quick Edit. (See Image Below)
When you click the Edit link (Above), you can add columns directly from the List page. (See Image Below)
However, when you create columns this way, the column name is NOT the double encoded version of the text you entered. It is a random string of numbers, letters, and sometime non-alphanumeric characters! (See Image Below)
There is currently no fix for this so please vote on this issue at User Voice for Office 365 here: https://office365.uservoice.com/forums/273492-sites-and-collaboration/suggestions/9756108-update-the-sharepoint-online-list-quick-edit-colum.
This is a pretty big issue so please vote for this and share to get visibility with the product team. Also if there are other scenarios where this happens please leave a comment.