I have for a long time been appalled by casual use of this word as trivial pejorative. When I first heard it a long time ago it was a fighting word. Just now I stumbled on this, the first time I have had my reaction to it confirmed.

"suck - O.E. sucan, corresponding to L. sugere "to suck," from PIE root *sug-/*suk-, of imitative origin. Meaning "do fellatio" is first recorded 1928. Slang sense of "be contemptible" first attested 1971 (the underlying notion is of fellatio). Suck eggs is from 1906. Suckling is early 13c. "

Slang sense of "be contemptible" first attested 1971 (the underlying notion is of fellatio).

Please clarify, Br Bill. I'll attest to it's use before 1971, but I'm not sure to which use this is referring.

I too think it was much older, even back into the thirties.
I took that from a site I use a lot was couldn't rememer site name of accurately. I find it just by searchin for "Etymology suck" in Yahoo search box. I'll go look for it and edit name in.
Edit: Here's the URL to site I got that from:
http://www.etymonline.com/s13etym.htm