Ferromancy means the manipulation of iron; it may be a branch of magic which relates to the manipulation of various minerals. It is also a synonym for mortal/manmade technology (usually modern).
Ferrum: Latin for Iron (Periodic Table of Elements: Fe = Iron)
-Mancy: Greek for Divination. In the books, "-mancy" usually refers to a type of magic, or magic in practical use (as in: Pyromancy [fire magic], Necromancy [death magic]; also used when Harry sarcastically refers to wizard Peabody as a "Bureaucromancer" & when he calls Mac "a master Beeromancer")
- Magic Suffixes Technical Breakdown: "The suffixes -kinesis and -kinetic seem to have been naively derived from the well-known "telekinesis"; they actually mean "motion". Literally, "Hydrokinesis" would be the power to move water. Similarly, -mancer and -mancy seem to have been derived from the well-known "necromancy", even though in the original Greek they come from the word mantia, meaning "divination". The "-mancy" template originally referred to the practice of divining the future using whatever the prefix was as a medium. So a classical necromancer would ask important questions of a dead person's spirit, a pyromancer would look for important symbols in flames, and so on. (It could be argued) that the proper suffix for someone magically manipulating a substance, force, or entity would be "-urgy" and "-urge" which derives from érgon or "work". This, of course, does not change the fact that in practice, "-mancy" and "-kinesis" are ubiquitous and "-urgy" is nearly unheard of." (Source: "Whatevermancy" )
In the series Edit
Fan speculation Edit
It is speculated that in the "Dresdenverse" that having an ability to sense magic energies (or a specific form of energy) is required in order to learn how to work with said energy. Thus, those who use spellcraft often have "The Sight" or some variation of it in order to interact with magical energies. Thus while the root term "-mancy" technically is specific to divination by its root definition (mantia: Gr), in the Dresdenverse it may relate to being able to physically sense how the energy in question moves, grows, expands and decays, and thus alows the practitioner to interact with said energy thus bridging the gap between perception by intuition to include manipulation, use, and crafting of energy.