Halliday & Matthiessen (1999: 286):
Almost all technical terms start out as grammatical metaphors; but they are grammatical metaphors which can no longer be unpacked. When a wording becomes technicalised, a new meaning has been construed — almost always, in our present-day construction of knowledge, a new thing (participating entity); and the junction with any more congruent agnates is (more or less quickly) dissolved.