What's the etymology of "props"?

Props can mean compliment / respect / credit, for example:

Erika gets props for the great work she did on the music.

Wiktionary states that props is:

(slang) proper respect or proper recognition for another person; an expression of approval or a special acknowledgment; accolade or accolades; praise.
- I've got to give props to Roger for the way he handled that situation.

How did this word come about? What is its etymology?

According to Etymonline:

Props as slang shortening for proper respects (or something similar) appeared c.1999.

There is an intermediate form propers, used in Otis Redding's Respect, made popular by Aretha Franklin.

give me my propers when ya get home

Props is originally hip-hop slang, derived from propers, both similarly meaning due respect.

According to The Rap Dictionary ("the oldest and ultimate resource for looking up hip-hop slang"), props is:

An abbreviation of "propers" or proper respects. A show sits on physical and non-physical props. At an award ceremony the winner gives props: "And I would like to thank...". "Cause this hip-hopper gets props just like a mobster" -- Da Youngstas featuring Pete Rock & C.L. Smooth (Who's the Mic Wrecka)

An older Hip-Hop/Slang Dictionary posted to alt.rap in June 1992 by Lee P Miller defines:

props : 1) (n) Proper respects.

The oldest use I found in alt.rap is from July 11, 1991 by Gregory Vincent Battle:

Now wait a second here. I have to give Hammer minor league props, even before "Hammer Don't Drown Em". I personally HATED Hammer when I first heard him. He stole rhymes (worse than Shy D, that fuck), and inimitable rap ideas ("yeahh boyeee"), and Too Big was more of a black Pilsbury Dough Boy than a sidekick. Shit, I'd kick him in the side :) Well, I got free tickets to his first concert tour and I enjoyed it completely. His show was pure energy. I think he might overdo it now with his 60+ dancers/backup rappers/DJ's. But hey, I still don't like him enough to buy one of those wick-wack rekkids.

The OED also says it's a shorted plural form of proper with a first quotation from the Chicago Tribune (July 1990):

I was one of the first female rappers, but I've always gotten my props.

The OED says propers is similar African-American slang for due respect, first quoted in the Chicago Daily Defender (January 1971):

A level of existence which affords each black man his propers—dignity, pride,..and the ability to govern his destiny.