The other day, I was reading a history of the Norman and Angevin kings, and came across the word kirk in an ecclesiastical context, which I had to look up, having no clue of its meaning. The Online Etymology Dictionary gave me this:
kirk c.1200, northern England and Scottish dialectal form of church, from O.N. kirkja "church," from O.E. cirice (see church).
I took its advice, and looked up church:
church O.E. cirice "church, public place of worship, Christians collectively," from W.Gmc. *kirika (cf. O.S. kirika, O.N. kirkja, O.Fris. zerke, M.Du. kerke, O.H.G. kirihha, Ger. Kirche), from Gk. kyriake (oikia), kyriakon doma "Lord's (house)," from kyrios "ruler, lord," from PIE base *keue- "to swell" ("swollen," hence "strong, powerful"). Phonetic spelling from c.1200, established by 16c.
One notes that both words, kirk and church, have the same etymological root in the Old English, cirice. But the Scots version, and its etymological predecessors, would all seem to be pronounced with a hard 'k'; the softening of the Middle English church seems to be a unique, derived, synapomorphy of the word tree.
So my questions are: What is this phenomenon called, exactly? Second, was it a general characteristic of the evolution of Old English to Middle English, this softening of hard consonants?