Signs

 Though the meaning or even name of various signs change over time the @ symbol started out meaning "at" in the 16th century as used by merchants to indicate pricing like 5 apples @ $2. Then in 1970 its use changed when the first email was sent though the meaning remained the same. Next we have the ampersand which used to be considered the 27th letter of the alphabet in the 1800s. When children would recite the letters they would end with "and per se and" which eventually slurred into the word ampersand. Last on today's list is the dollar sign, $ originally referred to the Spanish peso in the 18th century. It started out as "p$" then over time the "p" evolved into the straight line part of its form and merged with the "S" making it the $ we have today.