Periodt (period with an extra t) is an emphatic full-stop, declaring something is final and not up for debate. "It's the best song of the year, periodt." Roots in Black queer ballroom culture, now mainstream. Not concerning, just emphatic vocabulary. The extra T is for emphasis. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in.