Words for hill and related words in Celtic languages.
There are several Proto-Celtic words for hill: *brendo-, *brixs, *dindu- / dinnu-, *dumjo. *knokkos. *lettrek-, *mello-, *roino- and *tumbo-. *krakko- is a hillock or scab, and *krouka- is a mound.
Only *brixs and *knokkos appear to have descendents in the modern Celtic languages.

| Proto-Celtic |
*ardwos = high |
| Gaulish |
Arduenna = place name |
| Old Irish (Goídelc) |
ard [ar͈d] = high, height |
| Irish (Gaeilge) |
ard [ɑːɾˠd̪ˠ/æːɾˠd̪ˠ] = height, hillock, top, high part, elevation, head, rise, ascent
ardaigh = to raise, elevate, ascend, carry
ardaitheoir = lift, elevator
na farraigí arda = the high seas
sála arda = high heels
Ard-Aifreann = High Mass
Ard-Aighne = Attorney-General
ardaingeal = archangel |
| Scottish Gaelic (Gàidhlig) |
àrd [aːr̪ˠd] = high, lofy, tall, great, loud, chief, eminent, superior, supreme
àrd-bheinn = pinnacle |
| Manx (Gaelg) |
ard [ø(r)d] = high, towering, tall, big, loud, height, high place, fell, incline |
| Proto-Brythonic |
*arð = high |
| Middle Welsh (Kymraec) |
ard, art = hill |
| Welsh (Cymraeg) |
ardd [arð/aːrð] = hill, highland, top, high, upland |
| Cornish (Kernewek) |
ardh = height, high place |
| Breton (Brezhoneg) |
arz = high, elevated, lofty |
Etymology: from the Proto-Indo-European *h₃r̥dʰwós, from *h₃erdʰ- (to increase, grow, upright, high) [source], which is also the root of the Latin word arbor (tree) and words for tree in Romance languages [source].
| Proto-Celtic |
*knokkos = protuberance, hill |
| Old Irish (Goídelc) |
cnocc [knok] = hill, lump, swelling
cnoccach [ˈknokax] = hilly, lumpy
cnocán [ˈknokaːn] = little lump, mound, hill |
| Irish (Gaeilge) |
cnoc [kn̪ˠɔk / kn̪ˠʊk/ kɾˠʊk] = hill, mount
cnocach = hilly
cnocadóir = hillman, hillclimber
cnocadóireacht = hill-climbing
cnocán = hillock, heap
cnocánach = hilly, uneven |
| Scottish Gaelic (Gàidhlig) |
cnoc [krɔ̃xg] = hill, small hill, hillock, knoll, chilblain
cnocach [krɔ̃xgəx] = hilly, rugged, abrupt
cnocaireachd [krɔ̃xgɛrʲəxg] = rough hill walking, pacing
cnocan [krɔ̃xgan] = hillock, ball of fibre |
| Manx (Gaelg) |
cronk = mount, tor, hill,
crongan = mound, small hill, tuffet, tumulus, hillock
cronkan = knoll, small hill, hillock |
| Proto-Brythonic |
*knox = hill, mound |
| Middle Welsh (Kymraec) |
cnwch = swelling, protuberance, thickness, hump |
| Welsh (Cymraeg) |
cnwc = hillock, knoll; swelling, tumour, lump, knob, hump
cnocell = hillock, knoll |
| Cornish (Kernewek) |
krug = hill |
| Old Breton |
cnoch = hill |
| Middle Breton |
cnech = hill |
| Breton (Brezhoneg) |
krec’h = height, eminence, mound |
Etymology: from the Proto-Indo-European *kneg- (back of the head, nape, neck). The English word neck, and related words in other Germanic languages, come from the same root [source].
| Old Irish (Goídelc) |
bruinne = breast(s), bosom, chest; womb |
| Irish (Gaeilge) |
broinne [kn̪ˠɔk / knˠɔk / kɾˠʊk] = breast, bosom; brink, verge |
| Scottish Gaelic (Gàidhlig) |
broinne [brɤin̪ʲ] = belly, stomach; womb; bulge |
| Manx (Gaelg) |
brein = womb |
| Welsh (Cymraeg) |
bryn = hill, mount, rise, bank; heap, mound; prominence, highness
bron = breast, bosom |
| Cornish (Kernewek) |
bronn / brodn [brɔn: / brɔdn] = breast, hill |
| Breton (Brezhoneg) |
bronn = breast |
Etymology: from the Proto-Indo-European *brusni̯o- (hill) [source].
Another Breton word for hill is torgenn.
| Proto-Celtic |
*brixs / *brig- = hill |
| Gaulish |
*brignā, -brigā = hill |
| Old Irish (Goídelc) |
brí [bʲrʲiː] = hill |
| Irish (Gaeilge) |
brí = brae, hill |
| Scottish Gaelic (Gàidhlig) |
bre = hill, headland |
| Proto-Brythonic |
*breɣ [ˈbrɛːɣ] = hill |
| Welsh (Cymraeg) |
bre = hill, hillock, mountain, hill-country, upland, peak |
| Cornish (Kernewek) |
bre [brɛ: / bre:] = hill |
| Breton (Brezhoneg) |
bre = hill |
Etymology: from the Proto-Indo-European *bʰerǵʰ- (high,) [source].
The Spanish word breña (scrub, brush, rough ground), the Portuguese word brenha (scrub, complication, confusion) come from the Gaulish *brignā, via the Vulgar Latin *brigna (rocky terrain) [source].
From the same PIE root we get the English words burrow and borough, and words in placenames such as burg, burgh and bury, and also the German Burg (castle), the Danish borg (castle, stronghold), and related words in other Germanic languages.
| Proto-Celtic |
*krowko- = heap |
| Old Irish (Goídelc) |
crúach = stack, mountain, hill |
| Irish (Gaeilge) |
cruach [kɾˠuəx] = stack, rick, pile, (mountain) stack
cruachach = full of stacks
cruachadóir = stack-builder
cruachadóireacht = (act of) building stacks
cruachán = (small) stack; person of stunned growth
cruachóg = heap |
| Scottish Gaelic (Gàidhlig) |
cruach [kruəx] = pile, stack; round hill; clamp (stack)
cho seasgair ri luchag ann an cruach = as snug as a bug in a rug (“as snug as a mouse in a haystack”)
cruach-fheòir = haystack
cruach-mhòna, cruach mònach = peat-stack
cruach-sheangan = anthill |
| Manx (Gaelg) |
creagh = stack, furrow
creagh fendeilagh = barricade
creagh hraagh = haystack |
| Middle Welsh (Kymraec) |
krug, gruc, grvg = hillock |
| Welsh (Cymraeg) |
crug = hillock, knoll, cairn, tumulus, heap, mass, stack, group, company, multitude; pustule, abscess, boil, carbuncle |
| Old Cornish |
cruc = hillock |
| Cornish (Kernewek) |
krug = mound, tumulus |
| Old Breton |
cruc = hillock |
| Breton (Brezhoneg) |
cruc = hillock |
Etymology: possibly from the Proto-Indo-European *krā(u)- (to heap up) [source].
Words marked with a * are reconstructions.
Sources: Wiktionary, Am Faclair Beag, Online Manx Dictionary, Teanglann.ie, eDIL – Electronic Dictionary of the Irish Language, In Dúil Bélrai English – Old Irish glossary, Geiriadur Prifysgol Cymru, Gerlyver Kernewek, Dictionaire Favereau, TermOfis, English – ProtoCeltic WordList (PDF), Etymological Dictionary Of Proto Celtic
