Icky-pick is a very thick petroleum-based substance with very high flammability, and consequently is only rated for outdoor use, frequently direct-buried in the ground. An outdoor cable spliced onto an indoor terminal block is prone to leak the gelatin which is a fire hazard. The thick gelatin stains clothing and hands and is very difficult to remove. When fiber-optic cables are to be spliced, the gelatin must be removed with solvents and swabs to prevent fouling of the splice.
PIC is the abbreviation for Plastic Insulated Cable. The cable is filled with an icky substance. The filled cable itself, therefore, is called "icky-pic."