Marco Cimarosti scripsit:

>
> I though that h-digraphs were a relatively recent innovation
> in Irish spelling: in the uncial script (which was ubiquitous
> in Ireland up to at least the 1970's) aspiration is indicated
> by a dot over the letter.

H-digraphs seem to have been an alternate spelling in Irish
from at least the late middle ages. I have seen illustrations
of books printed in Irish from 1602 and 1616 which used the
h-digraphs in uncial script instead of over-dots.

--Ph. D.