1.They are supplying motor impulses to muscles of pharyngeal arch, which are both skeletal(facial) and visceral(laryngeal), so why only visceral in name?
Visceral is a derivative of the word viscus, which simply means "an internal organ of the body". I believe visceral is being used with this, more general, connotation.
2.Why the name special?
The word special is used because SVE nerves are involved with what are considered to be special senses, which is to say, senses that have "specialized" organs (and subsequently, "special" nerves) devoted to them. The special senses are: vision, hearing (and balance), smell, and taste.
To quote Wiki:
The distinction between special and general senses is used to classify nerve fibers running to and from the central nervous system – information from special senses is carried in special somatic afferents and special visceral afferents. In contrast, the other sense, touch, is a somatic sense which does not have a specialized organ but comes from all over the body, most noticeably the skin but also the internal organs (viscera). Touch includes mechanoreception (pressure, vibration and proprioception), pain (nociception) and heat (thermoception), and such information is carried in general somatic afferents and general visceral afferents.
Although this passage mentions afferents, (I'm fairly certain that) the usage of "special" regarding efferents carries the same meaning.