Difficulty or problems; the Troubles, any of various periods of civil war or unrest in Ireland, especially in 1919–23 and (in Northern Ireland) since 1968; the expression is first recorded in the 19th century as referring to the Irish rebellion of 1641.
never trouble trouble till trouble troubles you proverbial saying, late 19th century; another version of the advice that one should let well alone. (Compare Do not meet troubles halfway.)
a trouble shared is a trouble halved proverbial saying, mid 20th century; meaning that discussing a problem will lessen its impact.
See also do not meet troubles half-way.