Tom Walsh wrote:

> These often resemble kennings, to my mind.

How so?  Kennings can certainly be hackneyed -- and some kennings
may also be used as chevilles -- but in origin a kenning is a kind
of riddle, so it's actual content is something to focus the mind
on.  When C Chulainn tells Emer that he spent the night "i tig
fir adgair bar maige Tethrai" (in the house of a man who tends
the cattle of the plain of Tethra), "mag Tethrai" is a kenning for
the sea, and "bar Tethrai" is one for fish.  But Melia says that
the function of chevilles is "musical and metrical" as they are
"carrying little information":

"Classical Irish poetry seems to be connotative and designed
for hearing for the most part, rather than denotative and
designed for seeing.  In such a context, in which the listener
does not, indeed, cannot, go back to re-examine a line, but
must cope with and understand (in all senses of the word)
a performance of a poem, the musical and metrical effects
provided by chevilles, which by definition are carrying little
information, may be primary; the chevilles may be more than
a set of "empty figures" used by necessity to fill out lines
of a verse form too complex for its practitioners, but rather
one of the essential means by which that poetry achieved its
effects in its listeners."

> Daniel F. Melia. "Empty Figures" in Irish Sylllabic Poetry."
> Philological Quarterly 56 (1977) 285-300.

Thanks very much for that!  I hadn't read it before.