Origem

do sinal de interrogação, exclamação (em inglês):

Question Mark

Origin: When early scholars wrote in Latin, they would place the word questio - meaning "question" - at the end of a sentence to indicate a query. To conserve valuable space, writing it was soon shortened to qo, which caused another problem - readers might mistake it for the ending of a word. So they squashed the letters into a symbol: a lowercased q on top of an o. Over time the o shrank to a dot and the q to a squiggle, giving us our current question mark.

Exclamation Point

Origin: Like the question mark, the exclamation point was invented by stacking letters. The mark comes from the Latin word io, meaning "exclamation of joy." Written vertically, with the i above the o, it forms the exclamation point we use today.

Mais aqui. Fonte: Coisas