1
general::
1. Ruined, spoiled, as in Six months after the wedding, their marriage was on the rocks. This expression, alluding to a ship running aground on rocks and breaking apart, has been used figuratively for other disasters since the late 1800s. 2. Served over ice only, as in He always drinks whiskey on the rocks. The "rocks" here are the ice cubes. [Mid-1900s] 3. Destitute, bankrupt, as in Can I borrow next month's rent? I'm on the rocks. This usage, from the late 1800s, is heard more often in Britain than America.
American Heritage Idioms
2
general::
Phrase(s): on the rocks
1. Lit. [of a ship] broken and marooned on rocks in the sea. • The ship crashed and was on the rocks until the next high tide. 2. Fig. [of an alcoholic drink] served with ice cubes. • I’d like mine on the rocks, please. • Give me a scotch on the rocks, please. 3. Fig. in a state of ruin or bankruptcy. • That bank is on the rocks. Don’t put your money in it. • My finances are on the rocks just now.
McGrawhill's American Idioms And Phrasal Verbs