I don’t remember the exact lines in the movie, but if I interpreted things correctly the giraffes were supposed to be mating giraffes but all they did was walk around, hence the queer complaint by the trader.
DRY, you are a darling, but I am a little saddened by the Shakespearean quote that seems to be missing in your flirt. 
Why single out the word “queer” as anachronistic? NOBODY in ancient Rome spoke English, so EVERY word used by EVERY character in the film “Gladiator” was technically incorrect. True, no ancient Roman would have used the word queer… but no ancient Roman would use the words “a,” “an” or “the” either- there are no articles in Latin.
So… unless you think the movie should have been shot in Latin and shown with subtitles, it’s hard to see what your problem is!
Ask and ye shall receive.
OED says queer is commonly thought of coming from the German quer (MHG twer) but says it is “of doubtful origin” because time frames and usage don’t quite match.
The first cite for the primary meaning of “strange, odd” is from 1508 (Dunbar). The first cite for the meaning “homosexual” is from 1922 (from Practical Value of Scientific Study of Junvenile Deliquents). The usage in this case puts queer in quotes, indicating it was alread in use, probably as slang. The first cite for the meaning “to be fond of” is from 1953 (Burroughs), putting Johnny L.A.'s theory into doubt. There is also a definition of queer meaning “not in a normal condition; out of sorts; giddy, faint, or ill” first cited in 1781.
There is also a second entry for queer meaning “bad; worthless” with first cite in 1561. This usage seems to have lead to the idea of something being counterfeit (“queer money”).
The first cite for queer as a noun meaning a homosexual man is 1932 (Auden). The first cite for queerdom is 1965.
As a verb, the first entry for queer is “a. To quiz or ridicule; to puzzle. b. To impose on, swindle, cheat” with first cite in 1790. The second entry is “to spoil” (as in “to queer the pitch/game/deal”) with the first cite in 1846.
So, after all that, we don’t know where the word queer came from or why it first was used to mean “homosexual.” My guess would be it came from the usage of “odd, not normal.”
As to the giraffes, they were supposed to be mating giraffes, so the implication was that they did not mate because they were homosexual.
Problem? No, but you seem to have one (reading maybe?). I guess you missed the part where I posted:
Thank you JeffB, Mandelstam, and bibliophage for actually understanding and answering my question.
DRY: I am actually reading secondary sources and they critique Suetonius for those reasons.
The problem is the giraffes are supposed to be a mating pair. The guy is complaining that they won’t mate. All they do is walk around. Thus they are queer. Which is supposed to imply they are gay, but could have just meant they are strange.
FINE! FINE!
“It is my lady, O, it is my love!
O, that she knew she were!
She speaks yet she says nothing: what of that?
Her eye discourses; I will answer it.
I am too bold, 'tis not to me she speaks:
Two of the fairest stars in all the heaven,
Having some business, do entreat her eyes
To twinkle in their spheres till they return.
What if her eyes were there, they in her head?
The brightness of her cheek would shame those stars,
As daylight doth a lamp; her eyes in heaven
Would through the airy region stream so bright
That birds would sing and think it were not night.
See, how she leans her cheek upon her hand!
O, that I were a glove upon that hand,
That I might touch that cheek!”
–Romeo and Juliet, Act 2, Scene ii
[sub]Sorry about the hijack, guys, but if YOU would turn down a flirting opportunity with Diane, you must be quee…homosexual. Not that there’s anything wrong with that.[/sub]
Interesting. Which sources, if I may ask? (I’m always interested if there’s anything newly published that I haven’t heard about)
Fairness compels me to point out that there were certainly weaknesses in other contemporary sources (Tacitus, to name one).