That "rule of thumb" bit is a total myth and you should go gargle some 12 gauge mouthwash for this sordid assortment of half-truths.
The Chinese ideogram for 'trouble' depicts two women living under one roof.
From The Straight Dope forums:
The character people are thinking of is the very uncommon one 奻 (nuán). There's no roof, but they are together and the meaning is "quarrel, quarreling, foolishness, foolish, etc..." It's by no means the common Chinese word for trouble (烦, 问题, 等等...), but it's not non-existent either.
Speaking of dope, I thought maybe you were thinking of the 麻 in 麻烦, which is an ideogram depicting the drying of cannabis (大麻) flowers for use in Chinese traditional medicine. True story!
"Chinese sides vagina", so I really had to check.
At first glance I thought you were checking vaginas.
Foreigners carry handkerchiefs, London is foggy...