Proto-Basque: *ɦorci / *ɦośti
Meaning: 1 sky 2 storm 3 thunder 4 Thursday 5 rainbow 6 cloud
Bizkaian: osti 2, 3
Gipuzkoan: osti 2, 3, ost-egun 4
High Navarrese: ost-egun 4
Low Navarrese: ortzi 2, ortzantz, ihurtzuri 3, ost-egun 4, hortz-adar, ortz-adar, orz-adar, oltz-adar 5, ortz-egun 4, orzi-adar 5, (Hazparren) ortzi 3, orzi-adar 5, (Aldude) orz-egun 4
Lapurdian: ortzantz, ihurtzuri 3, hortz-adar, holtz-adar 5
Baztanese: ortz-egun 4, ortz-adar, oltz-adar 5
Zuberoan: ́ortze 2, orzantz 3, ost-égün 4, ost-ádar 5
Roncalese: (Isaba) ost-égun 4, (Uztárroz) orz-égun
Comments: Apparently {Urcia} (*ɦorcia) was an ancient name for the sky-god, like Jove/Jupiter, Zeus, etc., thus *ɦorc-egun or *ɦośt-egun 'Thursday'. See the discussions by Michelena (1961: 130, 363-4) and Trask (1997: 277-79). There is similar alternation of -rc- / -śt- in a few other Bsq words, e.g. *ɦerce / *ɦeśte ‘intestine’, *borc / *bośt ‘five’ (q.v.).
