Originally Posted by
Warmtoast
...but why Freedom 7 and Friendship 7 as titles for these spacecraft?
The "7" was the number of astronauts that took part in the Mercury programme (Carpenter, Cooper, Glenn, Grissom, Schirra, Shepard, Slayton) though Slayton didn't actually fly until the Apollo/Soyuz mission in 1975.
Each pilot was invited to come up with a name for his mission - the six that flew were Aurora 7, Faith 7, Freedom 7, Friendship 7, Liberty Bell 7 and Sigma 7.