Liz brought up the name Delt a few days ago. On further consideration,
I think that this proper name may indeed allow us to further understand
the noun "deiltre ~ delltre".
In "Togail Bruidne Da Derga" (§108 in Knott's ed.) we get a description
of the six cupbearers ("sé dáilemain") of the King of Tara, whose names
are Úan (foam, froth), Broen (rain, drop of liquid), Banna (drop of
liquid), Delt, Drúcht (dew) and Dathen (a word/name regularly paired
with "drúcht"). The majority of these names are ordinary nouns related
to water/liquid, thus appropriate to and symbolic of the cupbearers'
Delt is, according to DIL, the name of a river, which gives the
name/word a liquid credential. More interesting still, is Deltbanna,
whom the Dindsenchas identifies as the son of Drúcht (Google
"deltbanna" for the links) and the husband of the goddess of the River
Life (Liffey). Wetter and wetter! Deltbanna is a transparent compound
of delt + banna(e), the latter being the word we saw above meaning
"drop of liquid". Construing this compound in the usual way gives us
the meaning "drop of 'delt'". What is "delt"? Something watery, it
It looks as if "de(i)lt-re" might be a compound like "delt-banna".
What, then, is the second element -re? I suggest that it could be the
noun "ré", unstressed and with a short vowel as would be normal in this
position. "Ré" means generally an interval of time or space, but most
often a period of time. "Delt-re" could thus mean "a period of
'something watery'". In context, "delt" would make sense as "fog" or
Deltbanna = a drop of fog (what we call "fog drip" here)
de(i)ltre = a period of fog
That's my theory.