A delightful site managed by Jerry Hay features a lexicon of colorful nineteenth century riverboat phrases.
A couple of examples:
Well Stacked: Men will often use this term to describe the admirable attributes of a female, but that isn't its original use. As steamboats evolved from modest packet boats to multi-decked vessels of grandeur design, some had the appearance of giant wedding cakes going down the river. Some were stacked with five to six levels of cabin and lounge decks. These boats were considered well stacked. Another use for the term was in reference to the tall, ornate smokestacks of the fancy boats.
Outlandish Behavior: The origins of this phrase have some similarity to the word "hillbilly." In the 1800s all lands west of the Mississippi River was called the outland. As with boats on the Ohio River, steamboats hired local residents to serve as roustabouts. The men coming from the states of Arkansas and Missouri had a reputation for being hard to manage. These rough and tough fellows from the outland were rowdy and fights would often ensue. Over a period of time, anyone misbehaving was considered to be having outlandish behavior.