"There are only four feet between them."
Translation:Níl ach ceithre throigh eatarthu.
The full set of nouns that use a plural form following some numbers can be found in the 2012 Caighdeán, §9.3.2, page 159 — viz bliain, ceann, cloigeann, fiche, pingin, seachtain, trian, troigh, and uair. (Bliain, fiche, pingin, seachtain, trian, and uair use different plural forms after numbers than their usual plural forms.) For these nouns, one and two use a lenited singular (as usual), three through six use an unmutated plural instead of a lenited singular, and seven through ten use an eclipsed plural instead of an eclipsed singular. Uair, the only one of these nouns that begins with a vowel, gets a prefixed h following trí, ceithre, and sé. These same rules apply for 11 through 19 (modulo 10). Numbers 110 and higher that leave a remainder of ten when divided by 100 use the same rule as ten above; other numbers 20 and higher that are evenly divisible by ten use an unmutated singular (as usual); and numbers 21 and higher that aren’t evenly divisible by ten use the same rules (modulo 10) as one through nine above.
EDIT: The rules are also in the 2016 and 2017 editions of the Caighdeán (§9.3.2, page 146).
An Caighdeán Oifigúil (http://www.oireachtas.ie/parliament/about/rannoganaistriuchain/ancaighdeanoifigiuil/) is only made available in Irish. I'm not aware of an English translation.
(I see that the 2017 edition is now available at that link. I haven't had time to see what changes have been introduced).
troigh, f. (gs. ~e, pl. -ithe).1. Anat: Foot. Ní rachainn fad mo throighe, ón troigh go dtí an tsáil, ina araicis, I wouldn’t stir a foot to meet him. 3(a).2. Step. Dá dtéadh sé troigh tharstu, if he should step beyond them, try to take precedence over them. Tá sé ar troigh gan tuairisc, no one knows his whereabouts. 3. troigh stoca, vamp of stocking. 4. Meas: Foot. troigh ar fad, a foot in length. troigh chearnach, chiúbach, square, cubic, foot.