Cnósach Focal ó BB p109 has this:

This is a saying meaning "luck turns to the true gambler at crockcrow", as glossed there.
What does this saying mean, though?

Le glaoch an choiligh is ea a screadann an fíorchearrbhach. = With the call of the rooster screams the true gambler.

Mar a déarfainn as Gearmáinis: Hinten ist die Ente fett.

I'm thinking the first r is slender in fír-chearúch, explaining Brian Ó Cuív's transcription. There isn't usually a crossover of palatalisation like this, but I think /j/ and /x'/ are the most likely to have slenderisation before them.

You probably know this or have seen this already but Ó Dónaill has "fír" as an alternate to "fíor".

Fíor can be slender to match the following consonant and even make the following consonant part of the same syllable.

So Fíormhaith can be said as fíorbh-aith.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal