What is the origin of "sucker" and "it sucks"?

I think it is clear that a sucker means somebody who is naive or gullible, while it sucks means “it is bad”, but I wonder where these two terms come from and what they mean originally?

Could sucker actually mean a baby who was just born and therefore, naive and can’t tell if somebody is lying to them? If so, then what about it sucks?

etymonline has for suck:

O.E. sucan, 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).

and sucker:

“young mammal before it is weaned”, late 14c., agent noun from suck. Slang meaning “person who is easily deceived” is first attested 1836, in American English, on notion of naivete; the verb in this sense is from 1939. But another theory traces the slang meaning to the fish called a sucker (1753), on the notion of being easy to catch in their annual migrations.

Short for "cock sucker", which is the days of non-political correctness and rampant homophobia was a serious and widespread insult/put down. "You suck" having the "cock" understood.