The Chinese symbol for faith xin also means trust.
The Chinese character for faith shows a man ("man" radical at left) standing by his words (at right). So "stand by your words" = trust or faith in Chinese.
When faith is used as in "conviction", it is represented by two words in Chinese "xin4 nian4".
Another meaning of xin is "true; truthful".xin is also a (written) letter since only "man" can "transmit words through writing".
As a verb, xin has the meaning "believe".
Some common phrases with the symbol for faith are
xin4 fen1 = envelope
xin4 fu2 = be convinced
xin4 ren4 = trust; have confidence in
xin4 xin1 = confidence
xin4 yong4 = trustworthiness
xin4 bu guo4 = distrust