What is the role of "dr-" at the beginning of certain adverbs?

Question

I'm referring to word groups like oben and droben, or außen and draußen.

Does the "dr-" represent something in its own right, perhaps a contraction of "dr-"?

Apparently, they lend some subtle changes or shades of meaning to the above-mentioned adverbs. How does that come about?

Answer 1

The adverb droben is a short form of "dort oben". It's contracted for "daroben" which is not used anymore. The word "droben" itself isn't very commonly used in everyday language though.

draußen is a popular adverb, meaning outside or outdoors. I'm not sure, but it could also have its origin from the word "dort" (in combination with außen) or as Takkat wrote: a contraction of daraußen (not a word in modern German).

There are other examples of adverbs starting in dr-:

• drunter (short for darunter)
• drin (darin)
• drüber (darüber)

Answer 2

Both examples come from a contraction of two words into one evolving from Middle High German:

draußen - mhd. dār ūʒen^Duden

or, in your other example from

droben - dort oben^Duden

Examples where both variants coexist are

dran - daran, drüber - darüber, drum - darum, drauf - darauf [...]