The original version, Collegiate Shag, originated in New Orleans and has been known at times as the "Flea Hop." It was popular in the early 1920's and pre-dates the Lindy Hop. It was primarily danced to fast ragtime-jazz type music.
Collegiate Shag has split, over the years, into various styles. The Collegiate and Murray Shag can be mixed with basic swing patterns and thus becomes "Swing Bal." The Carolina Shag was an offshoot of the Collegiate Shag, in the 1930s, and, today, is more of a swing dance-form than a Shag dance-form. The Saint Louis Shag is more of a speed dominated competition shag, which is different than the Collegiate, Carolina and Murray Shags. The Balboa was a more subdued version of the Collegiate shag, which still shares many similarities today.