What's a drib and what's a drab?

I mentioned to my daughter that some of the things I had ordered from Amazon were arriving in dribs and drabs. That gave me cause to wonder about the origin of the phrase. What was a drib and what was a drab? Upon investigation it seems that a drib was simply an alternative word for s drop or small quantity.

Drib was known in some English, Irish and Scottish dialects from at least the eighteenth century, and was most probably a variant form of drip or drop. It was taken by emigrants to the US and at one time was fairly common there. The English Dialect Dictionary quotes a letter written by Abraham Lincoln in 1862: “We are sending such regiments and dribs from here and Baltimore as we can spare to Harper’s Ferry”.

Whilst there are various meanings for 'drab' - such as an untidy woman, a minor debt or a something dull - none of them is likely to be relevant to 'dribs and drabs' and the phrsae is most likely just an echo of the word drib forming a duplicated compound similar to helter-skelter, hurly-burly and see-saw.