When people say "give props" to someone I know what they mean but do you know what the word "props" is from? Is it short for something? Thanks!

It's slang for "proper recognition". It was popularized in the 80's by rappers who shortened the term "propers" but was used as early as the 60's as an abbreviated version of "proper respect".

props = proper respect...

Well, I never heard of the expression but I'll take a wild stab at it.

If the expression means give someone what is due to them (respect, affection, etc.) then the expression comes from giving someone their 'propers', that is, what it is right to give them. See the song 'Respect' preferably as sung by Aretha Franklin.

If that is not the meaning, let me know. The only other prop I know of is the props in a theatre or television show, which is short for 'property', that is items owned by the theatre or production company and used in the show.

Prop - Etymology: Middle English proppe, from Middle Dutch, stopper; akin to Middle Low German proppe stopper
: something that props or sustains : SUPPORT

http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=prop

FIGURATIVE A lot of people use cigarettes as a sort of social prop (= to make them feel more confident).

http://dictionary.cambridge.org/define.asp?key=63428&dict=CALD

An item placed on a stage to create a scene or scenario in which actors perform a play in a theatre or motion picture. Usually the term "props" is reserved for objects with which an actor interacts (e.g. a glass, a book or a weapon). Larger items adding to the scene, (e.g. chairs) are considered part of the set.
They used the trophy as a prop in the movie.

http://en.wiktionary.org/wiki/Prop

a person or thing serving as a support or stay: "His father is his financial prop."

http://www.infoplease.com/dictionary/prop

a person or thing that one depends on for help or emotional support.

http://www.allwords.com/query.php?SearchType=3&Keyword=prop&goquery=Find+it%21&Language=ENG

'Give props' means giving good support.

The word 'prop' is cognate with the Telugu word
'praapu' having the same meaning.

The Rig Veda, which is now accepted to be 8000 years
old, mentions ships with 100 oars. The Buddhist Jataka
stories wrote about large Indian ships carrying seven
hundred people. They went around the world many a
times. Aithereya Brahmana, which is a part of the
Vedas, mentions Telugu people as one of the earliest
tribes. History says that Telugu King Samudra Gupta
went around the world several times.

Many cognate words have formed due to the interaction.
Some are given below. The second one is a Telugu word
having the same meaning which is being used for more
than a 2000 years:

attic - attaca. asset - aasti. beat - baadu. boat -
padava. bore - boriya. boy - abbayi. cavity - guvta.
cattle - goddulu. cheek - chekku. chin - chunbu. cut -
kota. dull - deela. elope - lepuka. fat - boddu.
foundation - punaadi. gale - gaali. lace - allica. link
- lanke. mask - musugu. master - mestri. mead - metha.
mouth - moothi. mud - matti. murky - muriki. nerve -
narav. oath - ottu. pale - paali. pan - penam. pap -
pappa. piece - pisaru. put - pettu. site - chotu. short
- chiruta. show - choopu. slice - cheelchu. suck -
cheeku. surprise - achcheraparachu. sweat - chewata.
theft - thoepidi thick - dukka. thread - thraadu. value
- viluva. veil - valle. vomit - vaamthi. upon - paina.
with - waththa. wonder - winta. yean - yeenu.