Words for dry and to dry in Celtic languages.

Old Irish (Goídelc)	tírim = dry
Irish (Gaeilge)	tirim [tʲɾʲɪmʲ] = dry, parched, thirsty, without mortar, solid, bare triomú = to dry
Scottish Gaelic (Gàidhlig)	tirim [tʲirʲɪm] = arid, dry; droughty, mealy tiormaich [tʲirəmɪç] = to dry, make dry, parch, dry up
Manx (Gaelg)	çhirrym [tʲɾʲɪmʲ] = arid, dry, waterless, sapless chyrmaghey = to dry, dry up

Sources: Wiktionary, Am Faclair Beag, teanglann.ie, On-Line Manx Dictionary

Proto-Brythonic	*sɨx [ˈsɨːx] = dry
Old Welsh	sech = dry, arid
Middle Welsh (Kymraec)	sych = dry, arid
Welsh (Cymraeg)	sych [sɨːχ / siːχ] = dry, arid sychu [ˈsəχɨ / ˈsəχi] = to dry; drain, deplete; become dry, dry up, wither; heal, wipe
Cornish (Kernewek)	segh [ze:h] / sygh [sɪ:x] = arid, dry segha [‘sɛha / ‘zɛhɐ] = to dry, wipe
Breton (Brezhoneg)	sec’h [ˈsɛːχ] = dry, unproductive (field) sec’hañ = to dry

Etymology: from the Latin siccus (dry, sober, thirsty) [source].

Sources: Wiktionary, Geiriadur Prifysgol Cymru, Gerlyver Kernewek, Dictionnaire Favereau