Oh dear, more thread drift!

I'll share my ideas: you may of course take them or leave them.

My understanding is that 'ballad' has various meanings.

In terms of the medieval forms referred to by Jack at 8;15, the 'ballade', which came from France, and was a lyric poem, typically had three eight line stanzas and a final four line stanza, though there were variations. The rhyme scheme for the 8 lines was typically ababbcbc. The last line of the final stanza is used as the last line for the other 8 line stanzas and for the final shorter stanza.

Francois Villon write a lot of these. They were popular in the 13th and 14th century.

Ballads, on the other hand, usually meaning narrative poems/songs, seem to have appeared in many parts of Europe in the late Middle Ages.   

One book I was looking at recently stated that 'carol' originally meant dance .... Just to express my personal frustration at getting to any 'facts' here.