Quiz: Remember the definition of mal de mer?
"young mammal before it is weaned," late 14c., agent noun from suck. Slang meaning "person who is easily deceived" is first attested 1836, 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. Meaning "lollipop" is from 1823.
To be in trouble; be in a bad situation (1970s+ Army)