What is the X in X-mas?
1610s, from Latin stridulus "giving a shrill sound, creaking," from stridere "to utter an inarticulate sound, grate, creak" (see strident). Stridulation is first recorded 1838.
stridulous strid·u·lous (strĭj'ə-ləs)adj.
Characterized by or making a shrill grating sound or noise.
Relating to or characterized by stridor.