What is rhyming structure called where a couplet interrupts an AB scheme e.g., ABABCCAB, does that style have a name? I heard some ancient ballads had the final verse go ABABCC "to end on a rhyming couplet resolution". However I've found 40 songs that have it on every verse. Can I read somewhere about this kind of stuff? These are variant examples:

COME ALL YOU SAILORS BOLD, = ABABCCCB
Come all you seamen bold,
And draw near, and draw near,
Come all you seamen bold
And draw near.
It's of an admiral's fame,
O brave Benbow was his name,
How he fought all on the main,
You shall hear, you shall hear.

JACK HALL = ABABAADE
I have furnished all my rooms,
lot by lot, lot by lot
I have furnished all my rooms,
lot by lot
I've furnished all my rooms
with black brushes and black brooms
And besides a chimney pot
which I stole.

CAPTAIN KIDD = ABABAAAB
Oh, my name is Captain Kidd,
As I sailed, as I sailed,
My name is Captain Kidd,
As I sailed,
My name is Captain Kidd
What law did still forbid
Unluckily I did
As I sailed.

THE SHAN VAN VOCHT = ABABCCCB
Oh ! the French are on the sea,
Says the Shan Van Vocht;
The French are on the sea,
Says the Shan Van Vocht;
Oh ! the French are in the Bay,
They'll be here without delay,
And the Orange will decay,
Says the Shan Van Vocht.

more variants:
ABAB CC BB
ABAB CC CBCB
ABAB CCC DCDC
ABAB AA ABAB
ABAB AA ACAC
ABAB AA AD
ABAC DD DC
ABAC DD DE
ABAC DD EC
ABCB CCB
ABCB DD E