What are these symbols for?

Ꜳꜳ Ꜵꜵ Ꜷꜷ Ꜹꜹ Ꜻꜻ Ꜽꜽ

These characters are in the Latin Extended D block. What are these things? I find out that they might complete a list of ligatures, but A ligatures (Æ æ) is in latin 1 supplement and there is no AI ai ligature.