Typically, the support level can be thought of as the level at which many buyers tend to enter a security.  The original low price level becomes a support area because investors will believe that prices will again rise above that level.  Typically, the resistance level can be thought of as the level at which many buyers tend to sell a security. 
15c congestion from, "action of gathering together.”
14c support from, bring up, up from under, portare "to carry." Sense of "that which supports" is from 1560s.