The ultimate origen of the word is obscure; the early forms appear with a palatalized initial letter, still surviving in such dialectical forms as “yate,” or in Scots “yett.”

In other dialects, however, it had been palatalized to a sibilant before i-sounds some time before the Christian era; e.g. in the Umbrian fa�ia = Latin facial.

This Lindelöf explains as due to the different quality of the h—in W.  S. it was guttural, hence caused breaking; in Nhb. it was palatal and hence the preceding a was palatalized to æ.

Just to what extent g, c, sc were palatalized in O. Nhb. is not definitely known.