FASCINATION ABOUT HAHA

an acquaintance who’s in his thirties and savvy, with good friends of any age, uses “hehe.” I come across it charming—he’s a perfect speller, and he’s a energetic, tidy author, and his “hehe”s are an odd mystery. I know very well what they imply: friendly, rather sneaky giggling at a shared joke. But why The one “e”? an express