Words for sedge, rushes and related things in Celtic languages.

Sedge can refer to any plant of the family Cyperaceae, particularly plants of the genus Carex (the true sedges) – perennial herbs with triangular jointless stems, a spiked inflorescence, and long grass-like leaves. Or, other plants that resemble true sedges [source].
Words marked with a * are reconstructions.
| Proto-Celtic |
*sexskā, *sexskis = rushes, sedge |
| Old Irish (Goídelc) |
seisc = sedge, rushes, marsh |
| Middle Irish |
seisc, seisg = sedge, rushes, a sedgy or rushy place
sescaid = thatches (with rushes)
sescann, seiscenn = unproductive ground, a march, swamp, bog |
| Irish (Gaeilge) |
seisc [ʃɛʃc] = sedge
seisceach = sedgy
seascann [ˈʃasˠkənʲ] = sedgy bog, marsh, swamp
seascannach = boggy, marshy
seasclach = sedgy ground, sedge |
| Scottish Gaelic (Gàidhlig) |
seisg [ʃesg] = sedge
seisgeann [ʃeʃgʲən̪ˠ] = sedge, boggy land, fen country
seisgeach [ʃeʃgʲəx] = sedgey place, reedy place, abounding in sedges, reedy
seisgean [ʃeʃgʲan] = marshy / boggy land, unproductie land |
| Manx (Gaelg) |
shiast = sedges, rushes |
| Proto-Brythonic |
*hesk = sedges, rushes (?) |
| Middle Welsh (Kymraec) |
hesg, hesc, hêsg = sedges, rushes
hescen(n) = sedge, rush
hescock = sedgy |
| Welsh (Cymraeg) |
hesg [heːsk / hɛsk] = sedges, flags, rushes
hesgen = sedge, rush
hesgog = sedgy |
| Middle Cornish (Cernewec / Kernuak) |
hesc(h)en = a bulrush, a sedge, a reed |
| Cornish (Kernewek) |
hesk = sedges, saw-grass
hesken = sedge, saw, saw-grass |
| Old Breton (Brethonoc) |
hïscen = sedges, rushes |
| Middle Breton (Brezonec) |
hesq = sedges, rushes |
| Breton (Brezhoneg) |
hesk [hesk] = sedges, rushes
heskenn = sedge, saw |
Etymology: possibly from Proto-Indo-European *sek(H)- (to cut, cut off, sever) [source]. Words from the same roots may include saw, sedge and sickle in English, Segge (sedge) in German, zegge (sedge) in Dutch and saks (a pair of scissors) in Danish [source].

Rushses can refer to: any of several stiff plants of the genus Juncus, or the family Juncaceae, having hollow or pithy stems and small flowers, and often growing in marshes or near water. Or, the stems of such plants used in making baskets, mats, the seats of chairs, etc. [source].
| Old Irish (Goídelc) |
lúachair = rushes |
| Middle Irish (Gaoidhealg) |
lúachair, luachair = rushes, rushy place, marsh |
| Irish (Gaeilge) |
luachair [l̪ˠuəxəɾʲ] = rushes, rushy place
luachrach = rushes, rushy place, abounding in rushes, rushy |
| Scottish Gaelic (Gàidhlig) |
luchair [l̪ˠuəxɪrʲ] = common / compact rush (juncus conglomeratus)
luchair [l̪ˠuəxrəx] = rushy, pertaining to rushes |
| Manx (Gaelg) |
leaghyryn = rushes
leaghyragh = rushy |
Etymology: perhaps from Proto-Celtic *lowko- (bright, light) from PIE *lewk- (bright, to shine) [source]. Words from the same roots include light, lucid, lustre and lunar in English, lleu (light, brightness, bright), lluched (lightning, thunderbolt, fever) and golau (light, bright) in Welsh, and lagas (eye) in Cornish [source].
| Proto-Celtic |
*brīnika = stick |
| Middle Welsh (Kymraec) |
bruyn, brwyn = rushes
brwynnha = to gather rushes, to brush, to cover with rushes
brwynawg, brwynog, brywnoc = abounding with rushes, rush-like, made from rushes |
| Welsh (Cymraeg) |
brwyn = rushes, brush, something of no value or importance, a weak person or thing
brwynen = a rush
brwyn(i)ach = small or dwarf rushes
brwyna(f), brwyno = to gather rushes, to brush, to cover with rushes
brwynaidd = rushy, rushlike
brwynbapur = papyrus
brwyn(i)og = abounding with rushes, rush-like, made from rushes, marshy and rushy land |
| Old Cornish |
brunnen = a rush, a reed |
| Middle Cornish (Cernewec / Kernuak) |
brunnen, bronnen, bruinen = a rush, a reed
bruin = rushes, reeds
bruinic = abounding in rushes |
| Cornish (Kernewek) |
bronnen, brodnen = rush
bronn = rushes |
| Old Breton (Brethonoc) |
broin = rushes |
| Middle Breton (Brezonec) |
broüen, brouen, broen = rushes
broennenn = rush
broennec = rushy (place), rush bed |
| Breton (Brezhoneg) |
broen [bʁoːɛn] = rushes
broenenn [bʁoːɛn] = a (piece of) reed
broeneg [bro.ˈɛ.nːɛk] = rushy (place), rush bed
broenna = to look for rushes, to stuff with rushes
broeneg = land covered with rushes, rush bed, rush meadow, rush grove
broenek = covered in rushes |
Etymology: from PIE *bʰrugh-no- (twig) [source].

Sources: Wiktionary, Etymological Dictionary Of Proto Celtic, In Dúil Bélrai English – Old Irish glossary, eDIL – Electronic Dictionary of the Irish Language, Teanglann.ie, Am Faclair Beag, An etymological dictionary of the Gaelic language, Fockleyreen: Manx – English Dictionary, Online Manx Dictionary, Gaelg Corpus, Geiriadur Prifysgol Cymru, Lexicon cornu-britannicum : a dictionary of the ancient Celtic language of Cornwall, Gerlyver Kernewek, Devri : Le dictionaire diachronique du breton, Geriafurch, TermOfis