Celtic *longā 'boat, vessel' (updated)

Celtic *longā 'boat, vessel' is attested in Welsh llong 'ship', Old Breton locou 'vessels, vases', Old Irish long 'vessel, (little) vase, ship', to which corresponds the Gaulish toponymic element Longo-¹. There's also Cisalpine Gaulish (Todi) lokan /longan/ 'cinerary urn', an accusative form where /ng/ is rendered as k.

Although some authors have suggested a loanword (with reanalysis) from Latin nauis longa 'warship' (lit. 'long ship'), specialists such as Matasović² think this is a genuine Celtic word without IE etymology, which I consider it to be a cultural loanword from North Caucasian *leqˀV 'a k. of vessel' (NCED 1511), where the ejective stop became prenasalized.

Also related is Latin lanx 'dish, plate'³, apprently borrowed from Etruscan in account of its vocalism (lack of distinction a/o). 

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¹ X. Delamarre (2008): Dictionnaire de la langue gauloise, p. 206-207.

² R. Matasović (2009): Etymological Dictionary of Proto-Celtic, p. 244.

³ This meaning is reflected in Tsezian.

Celtiberian boustom 'cowshed, byre'

Celtiberian boustom 'cowshed, byre', attested in the Botorrita I text, is a compound from Celtic *bow- 'cow' < IE *gʷōw- and *-sto- 'standing' < IE *sth₂-o-¹, formally identical to Old Irish búas 'riches, wealth (in kine)'². In Iberian toponymy, this word has descendants in busto, bustar 'meadow': Busto, Bustelo/Bustillo, Busdongo, Bustarviejo, etc³.

I think possible for Iberian buiśtin-, boiśtin-, attested in La Serreta texts, to be a Celtiberian loanword with reduction of unstressed vowels o/u > i.

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¹ C. Jordán Cólera (2004): Celtibérico, p. 64.

² R. Matasović (2009): Etymological Dictionary of Proto-Celtic, p. 71.

³ J.J. Moralejo (2007): Callaica nomina. Estudios de onomástica galega, p. 42.