Nirbat dergnat chuirmthigi...

Nirbat dergnat chuirmthigi
nir·fhácba do chlothaige;
nirbat muichnech i n-úathad
nirbat búaibnech sochaide.

(you should not be * flea * of ale house
you should not leave * your * fame
you should not be * melancholy * in * solitude
you should not be * boastful (one) * of crowd)

You should not be an ale-house flea.
You should not give up your reputation.
You should not mope in solitude.
You should not boast in a crowd.

This quatrain was jotted down by a scribe in the upper margin of folio 124a in the Book of Leinster. The expression "ale-house flea" is found elsewhere and seems to refer to someone who is annoying in a social gathering. In "Bríatharthecosc Con Culainn", which is inserted into "Serglige Con Culainn" in LU, we find "Nibat dergnat colla coirme hi tig rurech" (You should not be a 'drunken flesh flea' in the house of a king). The translation "drunken flesh flea" is suggested in DIL, but the phrase is probably intended simply as a variation on the "dergnat cuirmthigi" found above.

I have normalized the spelling slightly. The original is:

Nirbat dergnat chormthigi
nir fhacba do chlothuide;
nirbat muichnech i n-uathiud
nirbat búafnech sochaide.