Mysterious “_transient_ptk_patterns” in options table

I had recently encountered an error saying I have 705 autoloaded options at about 1 MB. The biggest one of them seems to be an option called _transient_ptk_patterns. It has a 490 kB size, autoload “on” and it has been called more than 1200 times. The content is a bunch of JSON objects. They have attributes like ID, site_ID, title, name, description, etc. Part of one object for demonstration:

"title": "Intro: Heading with image and two columns above",
"name": "intro-heading-with-image-and-two-columns-above-copy",
"categories": {
"_dotcom_imported_intro": {
"slug": "_dotcom_imported_intro",
"title": "_dotcom_imported_intro",
"description": ""
}

Has anyone encountered something like this? I was unable to find anything.