underlaughter

Probably derived from Middle English underlaughteren (“to smirk”), Middle English underlaughen (“to smile; smile with the eyes”), equivalent to under- +‎ laughter.

underlaughter (uncountable)

1. Suppressed laughter or laughing
   • 1922, Berta Ruck, The Subconscious Courtship, page 340:

     “Of course I am, thank you,” said Clover in a voice which also he would hardly have recognized, so gay was it with a ripple of underlaughter.

   • 1985, Daniel Albright, Lyricality in English literature, page 126:

     Herrick could not guide Corinna, and Pope could not guide Mrs. Blount, into a definite, satisfying image because their ladies were too multiform and subtle, too likely to recede into airy sourire, underlaughter, to permit any resolution, any pinning tot he wall; […]

• snickering

• underlaugh