I like this idea. It seems that as long as there is an event anywhere in your calendar (past or future) which contains similar text to what you are now beginning to type, a pop-up window will suggest that same event to you.
It seems that the only (and, perhaps the best) way to stop unwanted/irrelevant suggestions is to delete those un-wanted/irrelevant, pre-existing events which are being suggested to you. Note: Said 'pre-existing' events include future events that you have put onto your calendar.
Using the Calendar app in macOS, I found a fairly simple way to mass-delete these irrelevant events. My suggestion piggy-backs upon the suggestion above. As suggested above, into the search field in Calendar I entered the text which tends to bring up the pesky suggestions. All events containing that text were presented to me in a chronologically ordered list. I then quickly mass-selected any and all events containing that text. I did this using command-click to select multiple items; Or using shift-click to select a block of items. For example, I selected a block of items prior to a particular day (or between two dates) and deleted them all with one easy stroke of the delete key.
As stated above, my work on this project was accomplished in macOS on a Macintosh personal computer. I have not attempted this same project in iOS or in iPadOS or in the iCloud web interface.