the word 'spitball' is a transparent compound formed from two old english roots. the first element, 'spit', derives from the proto-germanic 'spitjan', related to the act of ejecting saliva. the second, 'ball', originates from proto-germanic 'balluz', referring to a round mass. the compound first appeared in the late 19th century, literally describing a projectile made of chewed paper moistened with saliva. its meaning later expanded metaphorically to describe an illegal baseball pitch altered by saliva and, as a verb, to the informal brainstorming of undeveloped ideas, linking the concept of something crude and hastily formed to speculative thought.

Structure: spit + ball spit (from old english 'spittan', meaning to eject saliva; functional role: base noun/verb denoting saliva or the act of ejecting it). ball (from old english 'beall', meaning a rounded object; functional role: noun suffix denoting a spherical object).