The story
See touch (“a little bit; a small amount”) and 'tism (“autism”). Attested as early as March 10, 2010 (see quotations); popularized in 2022 on the video-sharing social media service TikTok.
Etymology from Wiktionary, CC BY-SA 4.0.
touch of the 'tism
Today it means: A mild form or manifestation of autism. Full definition →