Old English sucan, from PIE root *sug-/*suk- of imitative origin (cf. Old Saxon, Old High German sugan, Old Norse suga, Middle Dutch sughen, Dutch zuigen, German saugen "to suck;" Latin sugere "to suck," succus "juice, sap;" Old Irish sugim, Welsh sugno "to suck"). Meaning "do fellatio" is first recorded 1928. Slang sense of "be contemptible" first attested 1971 (the underlying notion is of fellatio). Related: Sucked; sucking. Suck eggs is from 1906. Suck hind tit "be inferior" is American English slang first recorded 1940.
To do fellatio or cunnilingus; blow, GO DOWN ON someone (1928+)
[Sucks! as a contemptuous interjection used by British schoolboys is found by 1913]