Кстати Jūra у прото-Балтов изначально не означало Море, вот еще один аргумент.
Etymology
From Proto-Baltic [Term?] *jaur-, *jūr-, from Proto-Indo-European *h₂wer-, *ūr- with an added initial y, from *aw-, *awe- (“to wet, to moisten, to flow”) with a suffix -r. The initial *y may result from metathesis in *awer- (> *h₂wer-, *eur-), or from the influence of some other Proto-Indo-European root like *(e)rey-, *(e)rew- (“to flow”) (metathesized into *ewr-). The original meaning was thus “wet, swampy place” (cf. Lithuanian jáuris (“swamp”) < Proto-Baltic *jaur-), whence “lake” (still attested in old folk tales, and also in borrowings into Finnic: Livonian jõra, Estonian järv, Finnish järvi, Sami jaura, jawre, jávri) and finally “sea.” Cognates include Lithuanian jū́ra, dialectal jūrė, plural jū́ros, jū́rios, jū́rės (cf. Latvian dialectal jūre, jūris, plural jūres), Old Prussian iūrin, *jūren, *jūrʲai, Armenian ջուր (ǰur, “water”), Albanian hurdë (“deep place; pond; swamp”); without the initial *y, also Old Norse ūr (“drizzle”), ȳra (“to drizzle”), Latin ūrīnō (“to dive, to plunge into water”), ūrīna (“urine”).[1]